It's common to accidentally input a manufacturer wrong, have inconsistent capitalization among manufacturer names, or have an accidental extra character when you created or updated the product details. Each variation will show in the manufacturer filter drop down menu (shown below)
This field populates based off of the data in your product details page. If one product has a manufacturer misspelled, it will show in the drop down menu. If you want to remove duplicate or misspelled manufacturers, or want to remove a manufacturer altogether, please either upload all of the products and update the Manufacturer field to the correct value (leave it blank for the product if you wish to delete it and not update it), or follow the steps below to adjust them per instance.
First, you will need to search for the manufacturer that you wish to remove. It is recommended to do this using the "Products" tab so you can filter to all products status. This will show us any inactivate products as well. Once you search, go into each product and either adjust the manufacturer or clear out the manufacturer field.
Once all products have been updated, the manufacturer will no longer show up in any drop down menu.