This article explains how to reset an auto-incrementing field in TrackRecord.
Using the TrackRecord Type Editor, open up the item which contains the auto-incrementing field you want to edit. Double click on the auto-incrementing field (such as Identifier) and go to the Properties tab. Change the "Current counter value:" to 0 (or to whatever value you want the next item to equal). Click OK, OK and Close to exit the Type Editor.