How are win odds calculated?

Test Your Might

It’s baffling me – you would think that it’s calculated with the amount of wins a participant has, their win/loss ratio or yet I’m looking at a single man with 1649 wins and 613 losses that I apparently have a 72% chance of beating, along with yet another guy with 380 wins to 260 losses I seemingly have an 18% chance of beating. It just doesn’t appear to make any sense.
Unless, of course, it’s calculated by factoring in the stats of every player you’ve beaten/lost to, but that seems a bit too intricate.
Am I missing something obvious or are these win odds percentages broken?
EDIT:
For those of you looking for the response, the general (unconfirmed) consensus is that it’s calculated using a method very similar to the Elo rating system that computes skill based on who you fight e.g. you may gain more skill points defeating good players and shed less losing to great players and vice versa.
EDIT #2:
It is definitely an Elo-based points system; I have just noticed there’s a”Score” column on the participant game leaderboard these points must be given/removed dependent on how many your opponent has.

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