Lump sum payment for 3 months and got taxed for 20% instead of14%

I am a student and my department paid me for 3 months as a lump sum instead of each month that I usually get it . To my understanding, I got deducted on a 20% rate instead of the 12-14% that I would have for monthly payments. 

 

In which form can I check for the refund? How do I know that turbotax knows?