2011-04-26 19:13:13.18 Backup Log was restored. Database: QAI, creation date(time): 2008/02/12(11:37:56), first LSN: 24837:114963:1, last LSN: 24922:13456:1, number of dump devices: 1, device information: (FILE=1, TYPE=DISK: {'E:\SQLBACKUPS\QAI_logshipping\QAI_20110415214601.trn'}). This is an informational message. No user action is required.

I think the calculation would be 24922-24837 = 85