Hi
The capacity is derived by the system by simply multiplying the number of allowed stacks by the stack height, so in your case:
99 x 99 = 9801 hence there is no available capacity in the bin.
You could just amend either the number of stacks and/or the height, but this would only be a temporary fix as my fear here (along with Jurgen), is that there is no stock showing in the bin from your first screen shot.
Can you please confirm that your bin does not contain any stock ? If so, we need to try and understand why the capacity usage has not been reduced when the stock was removed.
Cheers