If you run the "acpi" command, does it agree with the popup? If so, then your battery is lying to the hardware. There's not a great deal we can do about that.
** Changed in: acpi-support (Ubuntu) Sourcepackagename: acpi-support => gnome-power-manager -- [ACPI] Wrong number considering minutes before extinction https://launchpad.net/bugs/57356 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs