Time remaining in "Downloading package files" window is overly precise

Binary package hint: update-manager

Ubuntu Gutsy

As I write this, Update Manager is downloading package files. What I see, in the space of about 30 seconds:
* "2h4m54s remaining"
* "2h4m52s remaining"
* "2h25m1s remaining"
* "2h24m58s remaining"
* "2h37m40s remaining"
* "2h37m38s remaining"
* "4h36m8s remaining"
* "4h9m33s remaining"

So Update Manager apparently doesn't know the time remaining nearly as precisely as it is pretending to.

What I should see:
* "about 2 hours remaining"
* "about 2 hours remaining"
* "about 2 hours remaining"
* "about 2 hours remaining"
* "about 3 hours remaining"
* "about 3 hours remaining"
* "about 5 hours remaining"
* "about 4 hours remaining"

Perhaps follow a pattern something like this:
* 0 ≤ estimate < 50 seconds: "about n seconds remaining"
* 50 seconds ≤ estimate < 50 minutes: "about n minutes remaining"
* 50 minutes ≤ estimate < 23 hours: "about n hours remaining"
* 23 hours ≤ estimate: "about n days remaining"

See also bug 74884. It may save time to fix this bug at the same time as bug 144455, which is the same problem in a different window with time estimates in a different format. (For consistency, the two windows should present their estimates in the same format. One way of fixing this would be to make them the same window.)