Keybow - specifying "+" and "-" on the numpad

I’ve completed my Keybow build and after some tinkering I’ve got a good layout figured out. The video editing software that I use recognizes the plus/minus keys on the top of the keyboard, and the plus/minus keys on the number pad as distinct, different keys.

When using the following command in my layout file, it will type a “+” in a text editor, but the editing software doesn’t react as if I’ve hit the “+” on the numpad.

function handle_key_08(pressed)
keybow.set_key("+", pressed)

Are there “special key” tags for the plus and minus keys on the numpad? After going through the Pimoroni guide and some Googling I haven’t been able to find anything. I’m hoping there’s an equivalent to “keybow.LEFT_SHIFT”, or something like that.