I had somehow accidentally modified a Vendor as a Transit location when playing with multiple warehouses 

Here with same actions made. How did you set on hand quantity correct under product valuation?

I have a similar issue.  Can you please tell me how to correct it in Odoo 13EE?  I can't seem to figure it out, I'm not a Odoo expert.

Thank you for your response, Ray.  The Product Moves doesn't seem out of the ordinary; I have the same number going out as coming in.

That said, If I had sold more items than I had, wouldn't that mean BOTH the current inventory valuation report AND the product detail page for that item would show a quantity of -1 (as opposed to the discrepancy between the two I mentioned earlier)?

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UPDATE: The Product Moves in conjunction with the Inventory Valuation for move dates pointed me to the issue.  I had somehow accidentally modified a Vendor as a Transit location when playing with multiple warehouses, which allowed me to force a receipt for quantity, but set a discrepancy with the valuation, which turned negative when I attempted to sell the product I "had" in the Product Detail (qty from 1 to 0), but "did not have" in the Inventory Valuation (qty from 0 to -1).