It depends on what scattergram you are viewing. But I can think of a few reasons that this could happen legitimately…
First is that a student took the SAT once and early but decided to focus on ACT and submitted that score. (I know kids with high ACT scores who didn’t do well at all on their first SAT.) So the school may only have seen a high ACT score even though the data set for the student includes the bad SAT score.
The student is foreign, still learning English, but brilliant at math. This will have an impact on grades and composite scores, but if the kid was a top 10 finisher in an international math competition, he or she will be interesting to top schools.
Any other variant of this. I have met a few kids who have incredible personal stories who are very capable students but whose stats, because of schooling in different systems, learning English, etc., are not going to fit a profile that compares to my kid’s, who followed a much more conventional path. Colleges don’t want kids who can’t do the work. If you don’t have an amazing back story, @stemmmm 's advice is best.