For anyone out of the loop: Size/key count is the new(ish?) metric which perhaps most accurately categorizes the keyboard hobby. E.g. if you look at reddit's r/MechanicalKeyboards, they're mostly <80% layout.

The classic full US keyboard with numpad nominally has 101 keys, HHKB style compact boards usually 60 or so. The bare minimum with all numbers and Fn keys may have as little as 40 keys. Hence:

  100%: full w/keypad,  
   80%: the main part plus cursors,  
   60%: just the main part, with 0-9,  
   40%: just QWERTY, no numbers at all. 

Yea, generally you have full size/108 key boards, tenkeyless (no numpad but other layout unchanged), then 75%/65%/60% which all condense the function row and arrow key block to varying degrees. TFA depicted an extremely condensed (and split) keyboard without even a number row. No idea what to call that.