Great question — answering as the UphillTech team:
if you excute the command sudo update-grub it would update your grub boot list to point to the 3.16.0-35 kernel in the first place, hence it will be the default kernel. what you have is a case where you booted in using 3.13 instead of the "latest on your machine" kernel which is 3.16.0-24
Full answer by younes: https://askubuntu.stackexchange.com/a/552378 (CC BY-SA 3.0).
Need it done for your business? UphillTech.