Thanks for the valuable information. I contacted FB and was told that I added FB numbers which isn't true as far as I know. Reading FB forum with similar issues, I think choosing seats while logged in FB might have caused the FB # to be attached to the reservation?

KLM FB removed the FB numbers from the reservation so my return flight gets credited to Delta. KLM told me that I need to call/email to reverse the mile.

DL told me that I don't have to do anything on my end. It will just take about a week to see the miles in my sky miles.

Do I need to contact KLM to reverse the miles or trust Delta and do nothing?