Glossary
Log sequence number (LSN)
The 64-bit, always-increasing identifier of every NTFS $LogFile record, encoding a wrap counter and the record's offset in the file.
A log sequence number (LSN) identifies each record in the NTFS $LogFile. Its high bits hold a sequence number that grows every time the circular log wraps; its low bits hold the record's position in the file, counted in 8-byte units. With the sequence-bit count from the restart area, the byte offset is (LSN << seq_bits) >> (seq_bits - 3).
LSNs only grow, so they give a reliable order to records that carry no timestamps. The same numbers appear outside the log: every FILE record in the $MFT stores the LSN of its last logged change at header offset 0x08, and index buffers carry one too. Details in restart area and LSNs explained.