You didn't beat them in terms of KAST (kills assists survive traded) %. Because you had only one more kill than them and the same number assists, the KAST was mostly affected by times survived and traded. And because they had 2 less deaths, I imagine that they must've been traded significantly more, enough to make that percentage a difference of 10. And also because they had 1 less kill but 2 less deaths, their K/D ratio is actually slightly better. It's a bit weird, but all of those stats probably contributed to a significantly higher tracker score. I hope this helps!