We noticed that at some point, the CiviDiscount reports for number of times a code has been used is reporting duplicates: i.e. for every one transaction that is made using a discount code, the code is being reported as having been used twice. So a user with one transaction will show up twice in the report. The only exception to this per code are transactions that were processed by a staff user though the back end.

Note: this is not happening with all codes but there seems to be no consistency or discernible different between affected codes and non-affected codes. I checked the fields in MySQL to see if it was an issue with the display or the way the data is being recorded and the each duplicate is separate, distinct records in mysql.

In the screenshot below, you can see that there were two separate records of a discount being used for one user who only has one recorded transaction. The records are 3 seconds apart.

CiviCRM 5.3.1 and CiviDiscount 3.5.