https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/spbcx/ne-spbcx-_spb_request_sequence_position?redirectedfrom=MSDN
_SPB_REQUEST_SEQUENCE_POSITION (spbcx.h) - Windows drivers | Microsoft Learn
The SPB_REQUEST_SEQUENCE_POSITION enumeration indicates the position of an I/O request in the list of transfers for an I/O transfer sequence.
windows driversspbrequestsequenceposition