Jarred,
I don't know how you got to these numbers, but they are absolutely wrong. When I go to the steam survey and only add AMD RX570 and 580 I get to 4.5 %, but In your table you show for all of AMD 3.9%.
Yeah, sorry. I just fixed them. I had an error in one formula row where it added up the wrong rows. It should have been 5.90% for August, not 0.7%. Still, AMD's RX 580 and RX 570 numbers are much lower than what you used.
This is the main GPUs page. 1.28% + 1.04% would be 2.32%.
I used the API page, under the DirectX 12 API. There's a 0.01% difference on the RX 570 number. I also included the RX 590, 560, and 550 along with the Vega cards (not mobile Vega, though). But then I sum up the entire column and divide the figures by that total to get the final "percentage of the whole" that I reported.
You probably used the Vulkan API, which is fubar numbers. I don't know why, but the Vulkan numbers are all basically double what they should be, across all GPUs. If you sum up the Vulkan API columns, they equal 194% to 196%. Here's my "corrected" Vulkan API data, the last few rows. To the right is the adjusted result (divide the main percentage by the total for the column), which correctly sums to 100%. I don't know what Valve omits, but it's problematic that Vulkan sums to 194% or more while DirectX 12 sums to around 90%.
Here's the same section using the DirectX 12 data:
And I didn't really think about laptop 30-series, which probably makes up a good chunk of that 21.7% (I assume you counted those?)
Yes, laptop data is generally included, for dedicated GPUs. I omit the AMD Vega Graphics integrated solutions, though, as those would skew the Vega + Polaris numbers. If you're wondering, total Nvidia mobile GPUs (at least those that are explicitly identified as mobile) for RTX 30-series accounts for 6.76% of the total, or about a third of all RTX 30-series. For the RTX 20-series, as well as GTX 16 and GTX 10, there's no clear way of seeing how many GPUs are mobile. AMD's integrated Vega Graphics solutions meanwhile account for 2.38% of all surveyed PCs, and most of those are probably laptops.