I have space for a 10'x10' wipe off mat at the main exterior entrance of building, but the interior foyer is too small for a 10'x10' mat. The interior foyer has enough room for a 3'x3' mat. At the second exterior entrance that is 2nd story walkway, I intend to use a 5' wide x 10' long wipe off mat. My question in the interpretation of the credit is; do I require a 10' wipe off at the exterior and interior entrance or a combination of 10'?