The target item for a label usually does not need to be claimed. However, claiming plays a role in the following cases:
Placing Driving Labels
A driving label sets one or more properties on the labeled item. The target item must be claimed. This includes flow arrow labels, unless the flow direction is already defined for the process run.
Placing Labels on Area Breaks
Placing a label on an area break causes a dynamic property to be added to the area break. For this to happen, the area break must be claimed.
If you modify a label, you do not need to claim it. However, modifying a driving label modifies the labeled item. Therefore, you must claim the item.