Skipped over that rule on page 20. It was briefly mentioned. Yeah, you're correct. It's a progress track for # of things you need to accomplish during each individual mission (not for the whole story card).
You have to admit though, they could have explained that a little better, ie from the example on page 19 there is no objective that needs 7. But now that you have pointed that out, that's good,. Because I was confused by this track.