Looks like the title is incorrect, and it's actually posts per day. At least, the graph shows a few days where the number goes down, so it can't be just the total number of posts (unless there was a wave of deletions outpacing the posts).
Edit: according to other people's comments, it is actually total posts, not posts per day. So my above comment seems to be incorrect.
Endless Sky is an amazing one. I've put tons of hours into it. It's a top down 2d space trading/fighting game, very similar to Escape Velocity if you've ever played that game.