I'm not sure what you're asking in terms of avoiding math gibberish. You add up all your game scores and you divide it by the square root of the number of games played, pretty basic stuff.
They went with this formula, I assume, because it walks a middle line between simply using a sum (which favors people just spamming the metaverse with lots and lots of quick games) and an average which would make it nigh impossible to see your score increase over time. Now, they could have gone with a much more complicated formula with scaled weights assigned to your most recent games, which would be far more representative for an actual competitive ladder, but then it would have been a formula that no one but people good at math could figure out easily. So they went with a formula that isn't perfect, but is basic enough that anyone who's had a basic math series can understand.
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