Congratulations on finishing the box challenge! By the end of the challenge your boxes end up pretty good and solid in every way, so I don't have much to comment. Lines end up being pretty accurate and confidence, your guesses for convergence are pretty accurate as well, only having some minor issues with the inner corner, and you've done a good variety of boxes through the challenge.

One minor thing I think I see is that the lineweight you add to the silhouette has a tiny amount of wobble at times, even if it's pretty accurate and confident overall. Just a reminder that you should be always prioritizing confidence over accuracy; a confident line missing the line you're adding weight to is preferable than a wobbly one that doesn't miss it. But like I said they're pretty good overall, so nothing super important.

Another thing is that to improve the minor line convergence issues you are having you can start thinking about the relationship between complete sets of lines, instead of thinking only in pairs. By doing this you'll be able to make more accurate guesses, and your convergences will improve. This is explained here, so give it a look.

Other thing that might help as well is experimenting with the order and method you use for drawing boxes, one that helped me to improve the inner corner issues to me was this one), so give it a try if you haven't yet.

In general like I said, pretty solid job on the boxes, so I recommend you to look into the advanced exercises so you can keep challening yourself. Good luck with lesson 2!