Yes, I believe what you have stated is correct. Basically, for a given tile, there are 4 "paths" that can be taken - north, south, west, and east. So each tile stores whether or not you can walk/interact to each of the 4 tiles located in those directions. So, if you don't want characters to be able to walk onto a tile, there should be no navigation lines going into that tile (or potentially an orange "Interact Only" if there's an object on that tile that can be interacted with from an adjacent tile).