The 0.8/0.5 refers to woodwork hits per match. Simple. It has nothing to do with shots/woodwork hit. He didn't explain how he got to 0.5, so I trust SI's sources. Actually, I'm starting to believe that he made the same mistake you are/were by forgetting that there are two teams in a match.
I don't know if your Portuguese is rusty, but the first paragraph in your linked site mentions the first round of fixtures. With the article being written in January, it's fair to assume that it's halfway into the season, so 17 of the 34 games in. Otherwise, provide better links