miss match on Virus Count

Hi ,

Good Day to All

We are using SEP 12.1 RU1 MP 1 on Win 2k8 Ent R2 Server in our environment, having 5000 clients across the Globe.

The Current issue is I have pulled Risk Distribution by Computer over a period of one month  on 20/12/2012 and one client is reported 25000 virus found and on 21/12/2012 I formatted the same system.

After one week (26/12/2012) again I pulled the same report for the last one month and it is showing 50000 virus  and the last virus reported on 19/12/2012.

I am quite surprising that why the count is miss matching, can anyone suggest ?

Thanks in Advance

Ajin