I've noticed that the percentage of the things you missed before is added on to your current amount carried from the first game. (ie. I had 77%, just did a mission I missed first time, and now it's 81%).
Does this mean that by the time I get to Chapter 5 and do everything I missed, I will be able to see my percentage as 100% before I actually complete the ending and watch the credits? (In other words, so I know if I haven't missed anything that time, before I finish it).