Hi Pete. What you are seeing is the default PolicyKit (polkit) authorization implementation that is part of the default Lubuntu install on the AtomicPi. To add the atomicpi user or any other user you have created on the system and replace root as the 'default' password prompt for authorization you can edit the file (need to use sudo, a root shell or otherwise ensure the text editor you are using has root privileges):
and add the user you want at the end of the last line of the file such as:
save the file and then when you launch the app in question next time such as time-admin, users-admin, update-manager, etc... via the graphical interface you'll be prompted for that user's password instead of root.
Other options (not necessarily recommended) are to set a root password and use that or uninstall polkit altogether.