There are 2 selection buttons on the front of the RMPT*0**. One is for the wiring type (2 wire or 2/4 wire), and the other is for the output selection (0..10V, 0..20mA and 4..20mA) as shown in the picture below.
On the other hand, the RMPT*3** only has the wiring selector on the front. This unit uses independent physical outputs for 0..10V and 4..20mA so the selection is made by wiring the desired output. Note that this unit doesn't support 0..20mA outputs.