@davidmt My friend and I used to play this as a two player game, one flying the plane and doing the bombing runs and the other taking care of the bandits - great memories
@sarajcox Make a fist with your right hand.
The knuckles and dips are the months - so first knuckle is January (high so 31 days) the first dip is February (low so less than 31 days) the next knuckle is March (31 days) - when you reach July, start again with the first knuckle.