Wonderful. Based on my experience with my own grandson who has Asperger's but doesn't want to learn to knit, with things he loves he loves to share. Perhaps your GS would like to make a video or tutorial of something he likes and could teach others. My GS loves to "teach" others. If he posted something online and you let us know we could give positive feedback, which I'm sure would be well deserved. He sounds like a wonderful boy who has a wonderful grandma. Kudos for both of you!
I should never overestimate my basic arithmetic skills.