How to stop auto-increasing number when editing a list item

I have used PowerApps integration to customise the data cards of the below fields, so that every time a new list item is added, a new auto increasing enquiry code and reference number is applied. In the below example, the last record had the enquiry code of 1004 and MI-SAP-23-1004

However, now when I edit an existing record, the enquiry code and reference number auto increases again.

How can I ensure the rule is only applied when adding a new item to the list??

For reference, these are the formulas I used for the enquiry code and reference number, respectively:

I would also welcome a different solution to achieve a auto-increasing reference number when a new enquiry is added.