My guess off hand is that the rating on your battery bank is 36000 milliWatt Hour, not milliAmp Hour.
Since you said you are not an electrician, let me take the opportunity to teach a little. Warning, this is gonna get long… Power is the ability to do work (operating the camera in this case). In electrical work, power is normally expressed in Watts (or multiples of that - more later). For smaller amounts of power, it is common to use milliwatts - or 1/1000 watts. In other words, 1,000 milliwatts is the same as 1 watt. Electrical power has several measurements. Two that I will talk about here are volts and amps. The common comparison that is used is to think of a water pipe with pressure and flow rate. The voltage is similar to the water pressure and the current measured in amps is similar to the flow rate in the pipe. Different devices electrical devices use different voltages. If you’re here is the US, the electricity in your wall outlet is around 117 volts. It does vary and is commonly referred to as 110, 115, 117, or 120 volts. The devices in your car (lights, radio, etc) operate at what is referred to as a 12 volt system. It’s actually around 13.6 when the engine is running. USB devices operate at 5 volts - plus or minus 0.25 volts. In my photo above the voltage is the top left number and is showing 5.12 volts so that is withing the specification. These days, almost all portable devices are using the USB standards for charging - which has simplified it for us as we don’t need special chargers for every device. USB-C adds a wrinkle to that that I might get into later.
On to amps (properly called amperes, but no uses that). Amps is a measurement of how much current is flowing. In the photo above, the second number on the left is current and is showing 0.19 amps. Contrary to somewhat popular belief, the device being powered will only draw as much current as it needs. As long as the power source is large enough to supply the required current, it will work. It does not matter how much larger the power source is, the device will only draw as much current as it needs. For example, during my Christmas light show, I have a Wyze V2 camera mounted onto my pixel tree and it is powered from a 5 volt, 70 amp power supply. The camera will happily draw only the about 0.2 amps that it needs. OK, that power supply is also powering about 800 pixels on the tree…
Watts is the measurement of total power. The number of watts is determined by multiplying the volts and amps. In my photo above the third number on the left is watts and is showing 0.96 watts. If you do the math, it’s not exactly right. I assume that is due to rounding off errors because the tester only displays 3 digits.
All of what I have talked about so far is instantaneous values - in other words, what is happening right now. Time does not figure into the equation. However for storage, time becomes a factor. Or to put it another way, now much power for how long. In most cases we use hours. That adds hour to the number. So 1 watt of power for 1 hour would be 1 watt hour (or WH). For smaller devices it is common to use milliwatt hours (or mWH). USB battery banks are very commonly rated in milliwatt hours. So your battery at 36,000 milliwatt hours (or cold be said to be 36 Watt hours) is a moderate size battery bank. The battery bank that is partially seen my photo is rated at 71 WH or 71,000 mWH.
The non-pan Wyze cameras draw between 1 and 2 watts for the most part. Cameras that have IR illuminators will draw more power when the IR LEDs are on. So making an assumption that for your test, the IR LEDs were on part of the time, your 36 WH battery lasting 19 hours sounds about right.
I said I would mention multiplies in power numbers. Starting with watts, for small or very large amounts of power multiplies are used to keep the numbers easier to work with. Here are the common ones:
1 microwatt = 0.000001 watts
1 milliwatt = 0.001 watts
1 kilowatt = 1,000 watts
1 megawatt = 1,000,000 watts
1 gigawatt = 1,000,000,000 watts (for you Back to the Future fans)
The last thing is the USB-C wrinkle I mentioned earlier. All USB interfaces prior to USB-C were dumb. By that I mean that the power source supplied 5 volts and the load drew some current at that 5 volts. USB-C has a mode called Power Delivery where the source and load are both smart and will coordinate with each other to deliver in some case substantially more power than standard USB can. Part of this is to increase the voltage from the power source. In the photo below, my phone is connected to my USB battery bank via a USB-C connection. You will see that the voltage has stepped up 9.15 volts and at that voltage the phone is drawing 1.60 amps for a total power of 14.6 watts. Note that the phone was 90 percent charged at the time. If it has been quite low, it would have negotiated with the battery bank to supply quite a bit more than that. The USB-C power delivery spec allows up to 240 watts, but most devices can’t handle that much.
Told you this was gonna get long…
At 70 years old, it’s been forever since I’ve done any math.