Reply to Mapping s4 knob controller type -> button?

watching video about creating sweep effects, running on TP2 for the s4 and i map the knob but when i go to choose what type of button, it only leaves the option for knob/fader. Any way of changing it to button?

edit: I also have a hercules RMX and when modifying the midi mapping in tp2, i'm able to use a knob in that case as a button, so i believe it just has to do with the s4, any ideas?