Firstly i would like to mention that you can get admission in Thapar university easily depending upon number of branches and its high rising fee structure. Now the thing is that in which branch you want to proceed. For a  branch of higher cut-off (computers/ece) you should score in the range 50-60 %  with above 80 % marks in your boards  examination. For (mechanical/electrical/EIC) range of nearby 50% will be fine.For(civil/Chemical) marks in the range of 40-50% will be needed. So to get a decent branch i would say target should be 50% of JEE exam.