Does this keypad work as a standard keyboard in BTT?
If so, using the "Generic Devices" approach might cause some problems because even if BTT recognizes for example key4, the keyboard will still send its default to the system.
You can check this by going to the keyboard shortcuts section in BTT. If BTT is able to recognize the keys there, it would be better to use that instead of the generic device approach.
You can make device specific shortcuts by selecting this:
