Just lay a wet rag on it for a couple of hours, then wipe. That should remove most, if not all of it. If there is still some residue, baking soda and a little elbow grease will take off the rest.
I keep my glass cooktop clean and shining with Bon Ami powdered cleanser, and it's very cheap too. Also keeps my stainless steel cookware looking new. For occasional stubborn food spills and cooked on foods on the stovetop, a razor blade widget is a good tool.
I would place a wet towel in the microwave and soak the spot until softended enough to wipe it off. You may have to heat the towel a number of times but eventually it will work.
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