Although the main character itself would fit in 16x16 grid he moves up and down during the running animation, so 16x16 won't do.
This is only one pixel issue so probably I should somehow squeeze him in, not sure why I decided otherwise - I guess I thought you could have multiple grids of different sizes and use them for different parts of the texture.
I have no knowledge of Unity though.
Probably I overcomplicated it; You know what? I'll take a look into that and fix it in v2 :)