Thanks for playing! I've added infographic tutorial into the games description to make it clearer now. I agree I should have make the mechanics a lot clearer. Hopefully this will help:
How to do damage?
Get the big white number on board to 0 but moving the dice to get the right sum of numbers on top of it
How did I get hit?
Either you ran out of time, got the wrong sum (you went into the negatives) or you fell out of the map.