I'm the calculator creator and the past 9 months or whatever I've never seen it off by more than maybe 2. If you enter everything in the proper cells (careful: it doesn't match the game display, it matches the downloaded ratings order), it should be fine. Sometimes the last few points do take a bit longer than the rest.
Anyway, now that you reminded me, I think I'll go in and change the calculator to round down the final ratings...it's even more accurate then. I'd change the cell order to match the game screen, but at this point that might confuse more people than it helps.
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