Delete all Records in the Table and then do a Compact &
Repair of your database.
However, please not that the only purpose of AutoNumber
Field is to provide uniqueness to each Record in the Table
and the actual value allocated to each Record shouldn't
matter. In fact, users shouldn't even see the values of
the AutoNumber Field and the values can become random and
even negative.
If the actual values allocated are important to you, e.g.
sequential numbers, you should not use AutoNumber Field.
HTH
Van T. Dinh
MVP (Access)