It only goes up to 12.
If you want more pitchbend range you have to do a little programming in the modulation matrix.
Start with the regular pitchbend range at 12. Then program a modulation matrix slot as follows:
Source = pitch bend
Destination = pitch
Depth = max
See if that gives you enough range. If not, add the same programming to a second mod/matrix slot. Adjust the modulation depth accordingly.