If you got that off of Google, via one of the celebrity net worth sites, you can almost entirely disregard it. They have no private knowledge of his worth, and commonly do a sloppy job of putting it all together. They're SEO spam sites designed for bulk to capture all the people searching for "kim kardashian net worth" or "how rich is kim kardashian?" etc.

His co-owner stake in id Software alone was likely worth $40 million (not after taxes of course) or more (ZeniMax raised an extra $105m for the purchase), and he had earned a fortune prior to that courtesy of 20 years of high selling games and relatively small development costs (some of which was burned on Armadillo Aerospace, perhaps up to $10 million total based on what Carmack has publicly said about the cost of operating it).

The high-priced buyout by Facebook likely increased Carmack's network significantly. $40m would be just 2% equivalent of the Facebook acquisition price. I wouldn't be surprised if Carmack owned 2% of Oculus.