What Do I Do With This?!

So my four-year-old just informed me completely out of the blue that 3x3 = 9 because 6+3=9.

Unaware that he even knew what "times" meant, I asked him who told him that (assuming he had heard it somewhere and just remembered it) and he said no one, he just knew it.

i called my husband at work to ask him if he had explained multiplication when I wasn't paying attention. He said Ben had his calculator out over the weekend and asked him what all the different symbols were. Tom said he explained that the "X" basically added numbers... like 2X3 is just like 2+2+2. He swears that's all he said on the topic.

Seriously. What do I do with this? His understanding of math at four blows my mind. I didn't do times tables until I was in third grade and even then, it was more memorization than anything else. I'm sure my grasp of what it really was was hazy, at best.

I don't want to turn math into work for him, he'll get enough of that all too soon at school... but he seems to enjoy it so much (ew!)... so I'm wondering what can I do with him to teach him new concepts and not screw up whatever they'll teach him in school in the coming years? Honestly, I'm kind of curious to see how far he could go before he doesn't understand something...

ETA: Being the skeptical mom that I am, I asked him what 4x3 was... "12." 5x3" "15"... 4x2? "8"... sheesh. He really does get it. WTH?