Statistics 4240 - Data Mining

In the example used in class for Naive Baye Prediction, I think the weights of evident of "present" and "absent" for the same X should add to 0 since the they are the log ratio of reciprocal numbers. But the slide shows that "0.51" and "-1.10" is a pair of "present" and "absent" weights of evidence. I don't know why...

One weight of evidence is, for instance, log(p1/p2), while the other is log((1-p1)/(1-p2)). These are not reciprocals of each other and will not
add to zero in general.