MF Inventory is "merchant fulfilled" inventory. Of course, this refers to the products in your warehouse, living room, etc. This is the stock that YOU want to sell for any given product (as opposed to stock that you've sent to FBA or another 3PL).
To know what your MF inventory levels are according to our records, there are a couple ways to do this. From the Manage Listings page, you can click on the "inventory" tab, like so:
Or, you can download the spreadsheet called "Quantity Update", and that will show you the current quantity that we have on record as available for a given product.
Please let us know if you have further questions about this topic or any others!