Microsoft CEO Steve Ballmer said on Tuesday that the company sold 4 million Windows 8 upgrades. While Ballmer may want you to think that’s a good number, it’s actually not.

Ballmer said today that Apple was a low-volume player in every market, except the iPad (Notice that Ballmer didn’t mention the iPhone even though that one product is worth more than all of Microsoft). He really should be careful what he says.

Microsoft’s has an installed base of 1.25 billion users. According to Ballmer’s own numbers, 4 million upgraded to Windows 8 in the first four days. That means that one-third of one percent of Microsoft’s user base upgraded.

Now let’s take a look at Apple. In its first four days on sale, Mountain Lion sold 3 million copies. Apple has an installed base of 66 million, meaning that 5 percent of Apple’s user base updated in four days.

It’s kind of like people don’t really care about Windows 8.