Sir, for ay 2017-18 in itr 3 sch tds 16a b/f coloumn need to be fill if not needed?

Sir, I am trying to fill ITR 3 AY 2017-18 in schedule TDS 16A ,where every thing has been filled at the time of validate ,the form asked to filled the "amount b/f in which TDS is deductedat sr.No1 in schedule TDS2." Sir i dnt have any brought forward amount why should i fill that.