The float arm position is determined by the position of the pump module in the tank port before the locking ring is fastened down. It has to be exactly right or the float may collide with various internal gubbins. The correct orientation is when the 'tongue' on the module top mates with the recesss in the port ring. I suspect it's possible to install it without them lining up.
You cam also test the float rheostat when it's raised up by putting an ohm meter to the appropriate pins on the pump's electrical connector shown below.
TC