Not specific to the 737, but 'standard' Boeing terminology is that the idle stop is 0 deg. TLA. Moving the thrust lever forward gives a positive TLA, pulling the reverse piggyback results in a 'negative' TLA (e.g. -75 deg.).
I don't recall the specifics of the 737, but full forward TLA is between ~50 and 60 deg. TLA, depending on the aircraft model.
Not to be confused with TRA - Throttle Resolver Angle - which is the signal read by the FADEC. TRA typically varies from ~5 deg. (max reverse) to ~85 deg. (max TO thrust), idle is ~35 deg. (again, specific numbers vary a bit with the aircraft model).