Like Wim sais...
Press Direct Acces and press the pedal. It will open the Assignable page (or press "Menu" button - Touch "Menu 1" tab page - Touch "Assignable" button).
Now, if you have the order like 1=Sustain, 2=Articulation1, 3=Volume, touch Menu (on screen) And you have the polarity.
PS: I have a pedal from Korg, I've used it on PA3, T5 and now on Genos. On PA3X was by default ok. On Yamaha (T5 and now on Genos) is opposite
But is working
I have to change it, because is very small, soft and I have to pull allways with my leg
Is this model:
which is the same like this from Yamaha