What does "Precision: White = nn%, Black = nn%" mean in a game broadcast by chessbase.com? The game "Salgado L, Iván vs Arroyo R, Jesús, 83rd ESP-ch 1-0", shows this annotation after the last move:


  Precision: White = 93%, Black = 18%.


What does that phrase mean?

Check https://es.chessbase.com/post/sabrina-vega-y-salvador-del-rio-de-angelis-campeones-de-ajedrez-de-espana-2018 for more information.
It surely is a measure of the quality of play, the deviation of the game from a "perfect game", as understood by the engine used in the analysis. A perfect move will lose zero units of measure.

I couldn't find a chessbase source, but here it is a similar question on lichess, in which the unit of measure is called a centipawn:

https://lichess.org/qa/103/what-is-average-centipawn-loss

Centipawn loss could also be expressed as percentage, but as your question is about precision, they should be the opposite amount. In your example for white, a precision of 93% equals 7 centipawn loss (7% of inaccuracy).