Every record in SQL Server transaction log has its own log sequence number or LSN. Log sequence numbers are ordered in such a way that changes related to the record with greater LSN occur after the changes related to records with smaller LSN. Each backup that is set in SQL Server has FirstLSN and LastLSN values. To find out all backup’s LSN values you need to look at its header using the following syntax:
RESTORE HEADERONLY FROM DISK = 'full.bak'