Those are the actual probabilities... it is literally in there name
Minimum is if you are a lucky bastard and get all the drops.... just like maximum is if your luck sucks and you only get the guaranteed drops. Average is just that the average. If you got everything on their drop rate. You didn't get any more or less drops than you should have statistically gotten.
Above average drops would be between min and avg while below average drops would put you between avg and max.