I have the bomb explosions set to 2 frames, they were set to 3 when I first looked which seems odd since there are only 2 frames to them, so I'll need to go look at the quest in the 2.11b10b to see if moving it to 403 changed that setting...
BUT
anyway even set now at 2 it is displaying more frames/tiles then that, which shows up in the explosions with enemy bombs (oct 3 and 4's) and when you bomb a wall.
EDIT;
Ok, I checked and in the 2.11b10b it was set to 3, so it didn't change the number.
Also keep in mind the 2.11b10b only had the one slot for explosion, no enemy or super sprite slot.
So what it's doing is using the 2 frames + 1 (the one after)