Media items or records in this batch - This will only link records with media items specifically in this batch.

Unlinked media items or records in collection - This will check all the media items in the whole collection that you have uploaded that are Unlinked (no record attached to them).

Any media items and records in collection - This will search the entire collection for ANY media item that matches the linking field you choose and attach the record (weather there is all ready a record attached or not).

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