Order notes are automatically added by the app during checkout for in-app analytics purposes. The notes look like this:

These are private notes invisible to the customer, but should you wish to remove them you can do so within the app block settings in the checkout editor:

By checking “True” for “Disable custom attributes” these notes will no longer apply to your orders and in-app analytics will be disabled. This setting must be checked for every Checkout Buddy app block in the checkout editor.