If you deleted all the records from the table and there is an Identity column in your table, You will see that when you insert a new record in your table then Identity column value starts from the last value of that column incremented by your step value.
If you want to start the Identity column value from the seed value after deleting all the record then you must have reset the Identity column value. Here, I am going to show you that how you can reset Identity column value in SQL Server?.
The following line resets the Identity value for the table so that the next record added starts at your specified seed value.
DBCC CHECKIDENT (yourtable, RESEED, reseedvalue) --For Example DBCC CHECKIDENT(' MyTestTable', RESEED, 0)