MIDI NOTES are general used for each zone of the trigger, 3 zone ride might have 3 MIDI NOTES, HI HAT even more, open, mid and close and foot chick
See here Example of Sample Rack midi note
Each zone of each dual zone are Velocity switch A+B, up to 4 sound for each Trigger 1 to 7, 2 midi notes for each triggers 1 to 7.
With Sd Cards
Dual zone snare Each zone have 2 sound velocity switch sound A+B,+ 2 midi note (total of 4 sound each triggers + 2 midi notes triggers)
Tom triggers are Dual zone, Each zone have 2 sound velocity switch sound A+B,+ 2 midi note (total of 4 sound each triggers + 2 midi note each triggers)
Cymbals triggers are Dual zone, Each zone have 2 sound velocity switch sound A+B,+ 2 midi note (total of 4 sound each triggers + 2 midi note each triggers)
Kick one zone, 2 sound velocity switch sound A+B,+ 1 midi note (total of 2 sound)
Hi Hat A:
Open; + 2 sound velocity switch sound A+B,+ 1 midi note
Mid ; + 2 sound velocity switch sound A+B + 1 midi note
Close; + 2 sound velocity switch sound A+B + 1 midi note
Hi Hat B:
Open; 2 sound velocity switch sound A+B +1 midi note
Mid; 2 sound velocity switch sound A+B +1 midi note
Close; 2 sound velocity switch sound A+B +1 midi note
HiHat Chick 1 midi notes, 2 sound velocity A+B
HiHat splash 1 midi notes, 2 sound velocity A+B
Hihat: Total of 8 midi note and 16 samples
With SD Cards =46 samples sound with velocity switch or simultaneous and 23 midi note each users kit
For 24 MIDI notes, I think most module handle these, unless limited trigger inputs, and you can assign no matter which sound on the cymbal or HIHAT, kick