Each loop contains 20 tiles, so 4 x 20 is 80, and there are 4 more tiles in the corners, for a total of 84.

Each loop contains 20 plus 2 tiles, but the corner tiles have been counted twice. So, 22 x 4 is 88, but 4 must be subtracted, for a total of 84.

The big square is 22 x 22, and the small square is 20 x 20, so there are 484 - 400 tiles, or 84.