What is column "reviewed"? Computes number on pre-made decks I haven't even touched.

[melbebs]

I see a column marked as "reviewed" with value X per deck and is described as the number of times I've seen a question from a specific deck. However, the value exceeds the amount of total cards in a deck and, I've only opened 1 deck out of my say 20 - so how can the column provide me a number???

I don't get it.