Since we recommend starting your install from the door and work your way back, I'd recommend starting on the door that is furthest into the garage, get it snug up to that door, and then work on the other door. Because each tile is 15.75", you will end up needing to cut the tiles for the second door in half to make them line up for the second door. Example: the second door is offset by 24", because the tiles are 15.75", you will have a gap of 8.25" one way or the other. To combat this and close the gap, you can cut a tile in half so that you can fill that 24" gap with a full tile and a half tile (15.75" + 7.875 = 23.625").
This creates a problem though in that the edge pieces will not attach to the cut tiles. So, what we'll have to do is send PEGGED edges for that outer section, as well as some of the metal clips that Swisstrax has that will allow you to connect the pegged edges to the cut tiles. Be sure when you cut these tiles that you don't go for exact measurements to snug them up to the door, but you instead cut them EXACTLY in half leaving the single center rib intact. It will make more sense when you receive the tiles and edges. Here are some photos from Swisstrax of what I'm talking about: