Special Variables for Curve Fitting: V_siga/V_sigb

Good evening,

I had a quick question about a couple of variables while performing a line fit. In the Curve Fitting.ihf documentation, V_siga and V_sigb are listed as "The probable uncertainties of the intercept (K0 = a) and slope (K1 = b) coefficients for a straight-line fit (to y = a + bx)." Is there additional information about how these are calculated and how I can interpret the output (e.g., whether a value of 0.11 indicates an 11% or 0.11% chance of calculated coefficient being due to chance)?

Thanks so much,
Chris