While waiting for slower players my Approach X40 enters shots I haven´t played.
How do I know which one to delete. If I delete the wrong one it looks like I´ve driven the green.
I am sorry your Approach X40 is adding shots improperly. It definitely should not be acting in that manner.
You are going to want to edit your shots in the Golf APP or by going online to Garmin Connect and editing your shots there so you can better see them and ensure you are not deleting the wrong ones.