Aquamist HFS-3 and MINI Tank GB

[BostonR56S]

Call me a noob, but 11/32" Drill Bit and a 1/8" NPT Tap, I looked at a tap chart and this matches for pairing together, but how is the tap smaller than the drill bit? I think I'm missing something with the "NPT"? National Pipe Thread/Tap? Is this a different standard than what a Drill Bit size is?

Also, where are you guys getting install instructions? I've been out of the loop.