In ConfiForms, since version 2.0 records are not deleted completely to keep the auto-numbering rolling correctly.

But sometimes there is a need to "start over" with fully empty form. Deleting all the record will not reset the sequence for auto-numbers, but there is a way to do that

We have explained this briefly in Release Notes#Version2.0.4

Here is a bit more detailed explanation

So, you will need to create or download a file with the following contents

{"data":"<list></list>"}

And use Migration and Recovery API to get it uploaded to your form, replacing everything in the dataset of this form with an "empty dataset"

This will reset the auto-numbering sequence, as well as remove ALL the data stored within this form