Trying to save new PLUs, but get warn message #2.

just a hunch here........ if you get an over limit warning on adding a new plu, what happens when you try to edit an already existing plu?
what kind of business is it used in?

my hunch would be that you have used all the available plus that are open in the memory.

I am able to edit a PLU through SP-5201. It's for a small grocery store. I can't seem to figure out how to delete PLUs.

You shouldn't be able to delete PLUs. They are a numerical link to a product. If you don't want that product any more then overwrite it or delete the name and price.

Ok, I'm starting to see my confusion. I get the error when I try and scan the bar code of an item. I now understand that that barcode is not the same as the PLU.