What part don't you get? (That gives me a starting point for adding more explanation.)
From your post, you have these relationships:
ProductionLog::ProductionID = ProductionData::ProductionID
RejectLog::RejectID = RejectData::RejectID
This part doesn't make sense to me. I think you left out some details: "While in the Offline Reject Log, I enter (in the portal) the production date, machine and station # and the lookup (to the table:Production Data) auto-enters the item code from Production Data. Problem is that we might change a mold in a station resulting in multiple matching records."
Apparently you have a relationship between RejectData and ProductionData? How is that relationship set up?
I Don't have any clue what role a "mold" plays in this look up.