Hmm actually i don't know.

After cheking its about 4 pixels wide, but then again its full res picture which i will shrink down to about 40 %, the size i post here.
I just read Red post again and i started with many mistakes. First my dun is not 2000x2000 A3 paper size. I put there John's grid over it and extended it. It is too big now and when i shrink it down 3x (for final map) it will be too small o.O
I am so bad in teamwork.... maybe this one won't be joined to the big dungeon i will work on it separately and start new one ?