how to change the time OS selection in grub ubuntu

Ubuntu 14.04 LTS

The default time during OS selection on dual boot system is 10sec.
There are various way to change the timer & here is one of the method.

source: http://askubuntu.com/

• Press Alt + F2
• Type command, gksu gedit /etc/default/grub
• change the GRUB_TIMEOUT value to 15 or 20 as required. (value in second) or Setting timeout to -1 will make GRUB wait indefinitely until you manually select an entry and hit enter, It should look like
  GRUB_TIMEOUT=10
• save it. Close gedit. Now open a terminal and run
  sudo update-grub