I’ve noticed that many episodes of many shows duration is very inaccurate. For example, the latest season of Curb Your Enthusiasm, the episodes runtime are 37-45 Mins. But Trakt.tv has all the episodes rounded down to 30mins. I’ve also noticed that in other shows, many episodes are rounded up. With such flawed data points, This creates an inaccurate total of watch content for that day. Personally I am someone who likes to track how much content I’ve watched in total for a given day.
If I’m missing 35mins from one daily total, that would create an even greater inaccuracy in the Year in Review total.

[Update] On further investigation it would appear that TVDB on the web has the same issue with inaccurate runtimes.
Perhaps you could include an option in episode pages for VIP subscribers to report and offer runtime corrections for those episodes.