Oh! They work (generally) like this......
Set the ISO or EI.
Point the meter at your subject & take a reading. It will give you a reading of a certain value, say it's 11.
Look at the calculator dial & set the dial for 11. The dial gives you a series of EV combinations & you choose the setting combination that give you the best(IYO) combination of speed & aperture.
I got outbid on it at the last minute Luckily there's lots of used spot meters on ebay right now. Another one is ending this afternoon. I'll give that one a bid here in a few hours.