Could you provide some additional detail?

Perhaps the delete button was only configured to remove the record in the list view, but that change was not deleted or saved to the backend.  You can try creating a simple SmartObject, generating a editable list view, and looking at the rules to understand how it is usually implemented.

I had SmartObject, List view, editable list view. But I haven’t set the rules in editable list view. Could you provide rules I should set in the editable list view?

Please see below:

https://help.nintex.com/en-US/k2five/userguide/current/Content/How-Tos/RequiredFieldsEditListView/Add-Required-Fields-Editable-List-View.htm

This tutorial will walk you through generating an editable list view, of which you can inspect the rules generated to understand how it is implemented on an editable list view.

If this is SmartBox the number will continue to increment as it is an Identity field in the database https://learn.microsoft.com/en-us/sql/t-sql/statements/create-table-transact-sql-identity-property?view=sql-server-ver16

To reset the auto number you will need to ask a dba to truncate the SmartBox table in the K2 database and then call 

DBCC CHECKIDENT('TableName', RESEED, 0)

Hi @kkpt 
Did any of these replies resolve your question?