Variogram model fit

[AlowWong]

Hello, I am trying to predict the air temperature by using the data from weather stations. The get_statistics method provides three criteria for the variogram fit, which are Q1, Q2, and cR. I may miss something about the explanation of these three values. Are these criteria similar to the mean error, root mean square error or root mean square standardized error?

I am also confused that the best R²_score is negative when using the demo codes of Krige CV to get the best parameters. Is it possibly caused by a few data points?

Thank you very much in advance!