Who the hell knows what UMd was or is planning to pay. It seems pretty evident that UMd has not paid a dime to the ACC up to this point, which is why the ACC is witholding money. If you are UMd, why would you pay anything now if youare in the middle of contesting the amount you should actually pay. From what I've read on this insanely well informed and in the know message board (key work, insanely)

is people thought UMd would ultimatley end up paying in the mid $20's, but not the full $52 they (and FSU) never signed up for.
I'm no fancy book learning lawyer, I'm just simple caveman, but I would think their first approach would be (and was) we shouldn't have to pay anyhting since there was no financial harm in our leaving, to which the ACC would counter (and did), BS you pay the full $52 per the bylaws, and they dance this dance back and forth - as they've done, and ultimately a compromise happens and they settle an amount somewhere between $20M and $52M (i'm guessing mid-upper $20's).
I would not say there is no financial harm to UMD leaving. As has been pointed out on this board, by several folks (not just ACCers), the ACC is losing a part of its presence within the DC market, and, is losing the Baltimore market altogether. That is not small potatoes.
What this really comes down to is procedure. Did the ACC follow its own bylaws in implementing the new $52M exit fee, or, not?
The ACC has to contest and fight for the full fee otherwise they leave a door open for others to balk at the exit fee. End of the day, all will settle without airing all the dirty laundry that goes on in the Game of Conference Realignment. A certain network with mouse ears will make sure of that.