Identity column value suddenly jumps to 1001 in sql server

In my table identity column values starts from 1 and so on. Identity column starts from 1,2 and so on and adding identity smoothly.


Last month I have upgraded my sqlserver from 2008 to 2012. and restart SQL Server 2012.

I have reviewed my table records are inserting in proper manner (auto increment) but suddenly it jumps to 11498 and onward . All the table in the database containing identity column.