Some time table identity value comes wrong sake of we delete manual entries, we added wrong data in edit mode or it takes next value of identity or some time automatically comes.
So in this case many developer are delete data or re-design to table structure (schema).
No need to do this you just clear data and run this command. Your data will be reset or reseed it will start from where you decided.
DBCC CHECKIDENT ( 'TableName',RESEED, 0)