Well, first, not all the entries listed are sharing something. So some of that discrepancy is the game entries, and such.

Second, the first entry is to share something in our archive, not the giveaway entry, so probably that makes up for some of the discrepancy as well.

I'm not entirely sure how that plugin works (I should look into that, I guess.) but I do know that it doesn't always register every time a post is shared. The most noticeable thing it doesn't seem to record is when people share a post via plugins for their browser like Shareaholic instead of the buttons at the bottom of the page. And sometimes the number of times a post was shared in a day doesn't show up until the next day. This is one of the reasons we require a link as proof. There's almost no third-party app that doesn't occasionally drop a post or two on the network(s) it covers.

And yes, absolutely. An entry that doesn't have a link to the post to prove it exists is disqualified.