FSS[4:0] contains the unread samples stored in the FIFO. So when the EMPTY is 1, the FSS[4:0] is 0. But when the OVRN_FIFO is 1, the FSS[4:0] should be 32 but it can't. So when FSS[4:0] is 31 we should check the OVRN_FIFO flag to judge the real unread sample number. Is that correct?