1. First I wanted to point out that our proofer is a bit on the sensitive side (not necessarily a bad thing). Typically you won't start seeing any delivery issues until you hit over 100k in text, but we just like to make sure you're keeping an eye on it when you're getting closer to the limit.
2. Next, the amount of text in a mailing is not just the visible text that you see in the email, but also the code required to make formatting changes to the text or to add in links, link names, etc. Sometimes you'll see that number jump up really high if you have a lot of text format changes or links.