Thermostat wiring - E/AUX

im currently trying to hook up my thermostat with the heat pump wiring diagram.
my old thermostat has 1 wire going into the terminal marked E/AUX.


BUT, during the label process it states to “Label these carefully!”

Am I supposed to label the wire W1 or * ???

It depends on if you want aux heat to run when the thermostat thinks that the heat pump isn’t keeping up. (W1)
Or if you want it to only run in case of an emergency. (*)

Personally, I’d split it up into 2 wires with a splice, and connect it to both * and W1.
Also be careful when you’re re-wiring, that C wire has a split in the insulation, make sure it doesn’t short against any other wire, or it will blow a fuse in your furnace.