This is the percentage that is not described. So if this number right here, if this number is, I don't know, 30%, if 30% of the variation in y is not described by the line, then the remainder will be described by the line. So we can essentially just subtract this from 1. So if we take 1 minus the squared error between our data points and the line, over the squared error between the data points, between the y's and the mean y, we have, we now have a percentage, this actually tells us what percentage of total variation, total variation, is described by the line. Is described, is described, you can either view it as described by the line, or by the variation in x. Is described by the variation, by the variation in x. And this number right here, this is called the coefficient of determination.