@pnoeric you press it once then start pressing other keyboard keys. You will see a key number appear in the upper corner everytime you press a key.

@Electromaster64

I am trying to get rid of the start+select=exit hotkey

So do you want to disable the "Hotkey" function all together?

input_exit_emulator_btn = 8

And you want it to exit the RetroArch emulator when you press button #8 on your generic USB controllers?

I think you have to set the hotkey to null so try added this to your retroarch.cfg

input_enable_hotkey_btn = "nul"

If that doesn't work also add this:

input_enable_hotkey = "nul"