last_lsn in a backup not matching with from_lsn in the next incremental backup

As per the example in…al_backup.html, the from_lsn in the incremental backup xtrabackup_checkpoints file should match with the last_lsn from the previous full or incremental backup. If it doesn’t, does that mean my backups are not correct? I ran one full backup and 3 incremental backups. None of the from_lsn match with the last_lsn in the previous backup.