When you have too many downloads to render in the downloads dropdown, Firefox apparently agglomerates the rest of the entries into a total. It says "Xh Xm left (X of X GB)", but it appears that the time left is a sum of the remaining time in all downloads, when it really should just be the maximum value of all of them. If you have 3 downloads, and they're going to individually end in 5 minutes each, it doesn't make sense to say 15 minutes left total because they're all download concurrently so the time left globally is the longest time rather than a sum. I've attached an example of what I mean. I hope I placed this in the correct topic, please correct me if it's wrong.