How to compute F1 score?
First you need to learn about Logistic Regression, it is an algorithm that will assign weights to different features given some training data. Read the wiki intro, is quite helpful, basically the Betas there are the same as the Ws in the paper. 

The formula you have is correct, and those value do seem off. It also depends on the number of significant figures you have, perhaps they are making their calculations with more than the ones they are reporting.

But honestly, you can't understand much of the paper unless you understand LR