"Best Score" when using Vicalib

[RoboBAR]

Hi,

I've been using Vicalib and after pressing "[" and heading back into the terminal i always see "best score:", sometimes the values are low, sometimes they're very high, I was wondering what the best score means. ive also noticed that these "best score:" displays show up in the terminal every-time that the identifying features in vicalib (while doing the calibration) turns red.

TL;DR
What is the "best score:"?
And what does it mean when the feature recognition turns red during calibration?