Look at the "perceptual reasoning index" and see if that score is higher than the others. Then look at the subtests. My kids who are both good at math, scored high on "matrix reasoning" and "picture concepts". Matrix reasoning in particular probably involves abstract reasoning, seeing patterns, etc. If he scored low in certain areas, that could pull down the FSIQ. If there are gaps between scores, the tester can report a general ability index, which just uses PRI and VCI, and relates better to giftedness than the FSIQ. It's also possible for kids to be gifted in some areas and not others, but if he is good in math, I would expect the PRI to be somewhat high.
