VB6 isn't in that index. Some people think the "Visual Basic" category is VB6, but it isn't. Tiobe is pretty clear about their methodology...though not TOTALLY clear, so you may have to read it twice. That category includes four things:

Visual Basic

They figure that Visual Basic might include some VB.NET, so they give it half of the returns from that one and from VB. A quick repeated sample suggests that both of those categories are actually 80% VB.NET and roughly 20% VB6 (slightly less, actually, as there were trace amounts of VBA in there, too).

Far worse, though, is that the four categories don't contribute equally to the ranking. VBA makes up nearly 50% of the results, while Visual Basic (which is 80% VB.NET) makes up most of the rest. The two categories VB and VB6 are trivial in comparison.

What that means is that, about half the ranking is VBA, most of the rest is VB.NET, and VB6 makes up between 10 and 20% of the ranking. So, VB.NET should have been ranked higher, and the Visual Basic ranking could then be called VBA+, though it would be lower. It's all there in the link to the methodology in case you'd like to replicate it. I only used Google Chrome, while Tiobe used a whole bunch of search engines. I doubt it makes much difference, though. Two categories account for the ranking, one of which is VBA, and the other is primarily VB.NET.