To delete auto-numbering properties for a field, select the auto-number listed under the feature class in the tree on the Geodatabase Synchronization Setup form.
With the auto-number selected, click the Delete button located at the top of the Geodatabase Synchronization Setup form.
A prompt will appear asking if you are sure you want to delete the auto-number. Click "Yes".
located at the top of the Geodatabase Synchronization Setup form.