Token Size

I have the MM and am playing DnD5e. I drag an orc onto a map and get a 1x1 unit size creature. I drag a Troll or Orog onto the map and get a larger one - a 2x2 unit creature.  Is that the correct size , as I cant see a sizing in the MM to relate to it? I can understand a Troll I guess, but am less sure on an Orog.  I have already upped the sizing on most maps from 5 feet per square to 10 feet per square - and am happy to have done so as it makes a 60 range spell more relevant - and bows.  Im not sure a 20' wide troll suits me. Yes I can amend it, but before I do, I wanted to ask if it was by design . 

The size of the token is the area it controls on the battlefield, rather than the literal size of the creature. Large creatures control a 10' square area, which is 2x2 squares on a standard grid, and each size up from there progresses to the next square size, 3x3, 4x4 etc. So yes, it is by design as per the standard grid size.