To test a routine dealing with Taxonomies, I had created several, and had referenced two of them in a multi-value field. When I tried to delete my test taxonomies, I got the following message on the Delete confirmation page:
This term is used by 2513 items, and may not be deleted.
The term wasn't really being used by 2513 items, it was only referenced by one. But, actually, the Node ID of the node that did reference it happened to be 2513.
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