# Glicko 2 Formula

I'm trying to learn about glicko 2 rating system . In that document, there is a formula in step 5, point 2 that says $$B = a - k\sqrt{\tau^2}$$ Can anyone explain what is the point of squaring the tau, then getting its root again?

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$$\sqrt{\tau^2}=|\tau|$$ ${ } $${ }$$ { }$