That is because of what javascript can represent:
http://stackoverflow.com/questions/307179/what-is-javascripts-highest-integer-value-that-a-number-can-go-to-without-losin
It isn't possible to show (accurately) a number larger than 9 007 199 254 740 992 so for some reason you get a number that is larger than that? The client checks for the value, if it is larger than the above number you will get that error message you referenced.
You should check your implementation, I can't think of a reason why the image crop module would calculate such a larger number. So your next step should probably debugging the microflows to find the place where this number is being calculated.