For the zone, I think. In TB's video it showed he had 16/20 main missions completed in the first zone. I hardly think that there would be only 4 in the whole rest of the game. It was funny though that TB thought that the first zone was the entire game, proclaiming that the whole game could be completed in around 8 hours .
There's not much at all after you get to the second area, it's 20 total (with 7 in the second area). He's right, if you rushed through it you could probably complete it in under 8 hours easily, but you'd be missing the point.
The story missions are SUPER short and the story really lacks a bit in terms of depth and development. It honestly feels like the story was rushed and left a little unfinished. There's more slave rescue quests than main mission quests. Note that I don't have any DLC (I didn't buy the season pass)