After the first data sync has run successfully, order sync from Prestashop can be deactivated as the sales-tracking from the module takes over.
To deactivate order sync, go to Improve => Modules => Module Manager
Scroll to the bottom and find the Clerk module under other. Click on Configure:
Scroll to the field named Settings For Data Synchronization and click on YES next to the text Deactivate Synchronization of Orders:
Scroll to the bottom of the page and press Save:
Your changes will then take effect.