Yeah sorry I didn't think much about numbers position but I kinda got used to them during development. My Idea was they are floating above empty squares at half the character's height. Initially I wanted to make a top-down game but when drawing the box I drew the isometric one and decided to go with it even though I had never made isometric games before :)
Another problem is that the walls aren't demarcated and that you must not push explosive boxes against the wall because you will never be able to get them out. Maybe it would make more sense if I had placed the acid pools at the corners of the map.