What do these buttons do?

I would like to know what do these buttons do? everytime i click on them the blue bar goes down .. can anyone tell me please?  :wtfvegeta: 

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this increase the time of double exp.
the blue bar indicate how many more point you for the three green buttons.
left to right of the green button is 10 minute increase, 30 minute increase, and 60 minute increase.
it will decrease the blue bar every you the buttons.

oh I see! Thank you very much for your answer!   

They're actually 3.5 times exp and they can stack with normal double exp to become 4.5 times exp.

really? so how does it work? like if im in a dungeon and I have the double EXP activated, i press the one on the far right for example so i get 4.5 more exp? for how long?

For as long as the duration you chose. So the far right is 60 minutes so 60 minutes.

I got it max out