Pray is the function that can help you get extra EXP when you're offline.
You can pray when you're online by tapping “Start” and your character will change into a resting gesture with a title of “Praying.” The amount of EXP recieved in Praying will scale to your character's level. You can only aquire offline EXP for 12 hours max. The amount varies, ranging roughly 8-10% of total EXP required.