ok, weve beeen keeping an eye on what they are opening/ calling /raising with and we have build a picture of how solid they are or are not.

Even if we havent always seen their cards, we,ve watched to see if they limp and fold to a min raise . therefore adjusting their ranges.

when we think we know what ranges they are on., and we have eliminated what we think they wont have , we see how many of flop cards hit their range and compare this to how we hit the flop, and we have a good guestimate of how often we are beat or ahead.