When you click on "Details" on Software Updater while it's downloading an update you only see the bottom half of the current file being downloaded. This is the behaviour regardless of the size of the window. Once the download finishes the terminal window that shows the install of the update displays normally.
1) The release of Ubuntu you are using: Ubuntu 16.10
2) The version of the package you are using: 1:16.10.7
3) What you expected to happen: Expected to see the whole line for the update being downloaded plus all the files already downloaded.
4) What happened instead: Only saw the bottom half of the current download.
ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: update-manager 1:16.10.7
ProcVersionSignature: Ubuntu 4.8.0-34.36-generic 4.8.11
Uname: Linux 4.8.0-34-generic x86_64
ApportVersion: 2.20.3-0ubuntu8.2
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Jan 26 20:54:31 2017
GsettingsChanges:
b'com.ubuntu.update-manager' b'show-details' b'true'
b'com.ubuntu.update-manager' b'window-height' b'648'
b'com.ubuntu.update-manager' b'first-run' b'false'
b'com.ubuntu.update-manager' b'window-width' b'726'
b'com.ubuntu.update-manager' b'launch-time' b'1485481744'
InstallationDate: Installed on 2015-10-22 (462 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
PackageArchitecture: all
ProcEnviron:
LANGUAGE=en_US
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to yakkety on 2016-10-16 (102 days ago)
Status changed to 'Confirmed' because the bug affects multiple users.