Reversal Posting (Urgent)

Dear Experts,

I am facing a peculiar problem, To one of the GL accounts, there are several Debit postings in current period i.e. but there is a credit posting, which has used T code FB08 (The T code used for reversal) to clear one document posted in previous period that is period 10.

1. What is strange is though its reversal posting (What I understand is that reversal posting can be created in same posting period) it has posted in period 11.

2. In month wise summary, I can see only debit balance; this credit posting is not showing.

Can any one explain why it has happened?

Thanks in advance.

Rg

VK