Very easy to spot, if queue file(s) into empty Transfers list.
Statistics > Disk Space > Total Competed Size would be equal to the number of queued files.
Gap size is calculated in 5 places, in 4 it is correct, and in the last one someone forgot to add 1;
in the function
void CPartFile::GetLeftToTransferAndAdditionalNeededSpace(uint64 &rui64LeftToTransfer, uint64 &rui64AdditionalNeededSpace) const
It should have been like (line 5657 in 0.49b)
uint64 uGapSize = cur_gap->end - cur_gap->start + 1;