Nah, like I said VGC gets some retail data and they use that to base their estimates on. Charts are used as well, but charts alone give you absolutely nothing but the order things sold in. If you're basing the sales on charts alone you'd just be pulling figures out of your ass. Much better to have estimates within an acceptable margin of error for physical sales, than just to have purely made up completely inaccurate digital sales added on to them. Besides, aren't digital charts usually just top 10s or something? So even if you had sales figures for one of the games on the chart (to use as a relative base for the others) it would still be completely useless for any game not in the top 10 that week.
Ok get that retail data but start estimating digital sales along with it. Its not hard to add 30-40% of sales. It tend to be high first week and then gradually slow down. And then depend on if there is any discount online.
Then find the game you want to see the sales of and multiply it by 1.3/1.4 (30%/40%) and there you go... the retail numbers are here for you, lol. But without any actual numbers coming from anywhere, we can't just make them up ourselves, since not every game has a 30-40%+ digital ratio, so we'd have games massively overtracked or even undertracked, it just isn't feasible to do it without any additional numbers.