Pretty self explanatory:
How much movement is there in period “x” from the top to the bottom? In perfect execution, what’s the most you can expect to get away with in the respective time frames?
Not surprisingly, pip efficiency goes down linearly as the time frames go by. This is explained intuitively by observing that higher time frames lend themselves to some form of retracement. 1m and 5m bars are most likely to complete without any wick.