DBCC CHECKIDENT is a handy command to reset the value of the identity fields. However, they behave slightly differently at different situations
What will be the outcome of the following command:
DBCC CHECKIDENT ('Table_a', reseed, 100) . Is it hundred?
Well, it depends. it depends on whether the table is brand new (vergin?) or got some data already. If the table ever had data, even if you truncate table, the identity will start from next value.
That is, if the table even had data the next identity value will be 101 and not 100.
Try yourself. If anyone gets a different value, check your code :)