I think i may have it. change this:
[ui-buttonmap] dl=KEY_NUM4 dr=KEY_NUM6 du=KEY_NUM8 dd=KEY_NUM5
[ui-buttonmap] dl=KEY_NUMMERIC_4 dr=KEY_NUMMERIC_6 du=KEY_NUMMERIC_8 dd=KEY_NUMMERIC_5
you can get all the codes like this:
sudo xboxdrv --help-key
Let me know how this worked out for you. It didn’t work correctly for me, but I think that may be because the keyboard I have connected has no numeric keypad. I’m working on finding a work around solution.