UGC NET is conducted for two papers for total marks of 300. Paper 1 having 100 marks  and paper 2 having 200 marks. 99.8 percentile means that 99.8 percent people have scored less than you. Based on previous year data, 99.8 percentile means you may have the score around 195 to 205 out of 300. We can't predict the exact marks as it depends on various factors like no. Of candidates appeared, highest score obtained etc.