ta = the test statistic for the null hypothesis that the slope = 0.
tb = the test statistic for the null hypothesis that the intercept = 0.
R^2 is the percentage of variation explained by the linearity.
Ideally, both ta and tb are not statistically different from zero, and R^2 is relatively low. If they are statistically significant, then there is a linearity issue with the gage.
Regarding the graphical analysis, the Bias = 0 line should fall within the 95% CI bands for the regression line. If it does not there is a linearity problem with the gage.