There was some confusion of what model Terminator the 'Arnie' version are. There is actually a mistake in T3 about this! It shouldnt have been made to be honest!
Terminator is a Cyberdyne Systems Series 800 Model 101, also referred to as a T-800 (in this film he's a T-850). "T-101" is a bastardized combination of model and series numbers, and is inconsistent with what appears in both other films. 800 and 101 are both numbers that refer to the "Arnold" terminator (model and series, respectively). But the "T" prefix is supposed to be followed by the model number (800), not the series (101). It's like referring to a Ford F-150 STX as an "F-STX." Even if what is meant can be inferred, it is a technical error, the kind the terminator would never make (especially in referring to itself).
Basically, Arnie is a T-800 (or T-850 in T3) and in the film he calls himself a T-101 which is incorrect.