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.

its total by day the dip is deletion

It's total

I think it's total posts. If you look at the list of instances and posts at the bottom it matches closer to total posts:

https://the-federation.info/platform/73

It's still epic and growing both in quality and activity, but it's still got a long way to grow. I feel optimistic. :)