It's kind of a difficult question to answer, I think, and I'm not sure exactly what the question is. Is it asking about:
a) quad-only sales figures for dual-inventory titles?
b) quad-only sales figures including single-inventory quads (Doors, Elvis etc.)
c) combined sales figures for albums that had both quad and stereo releases?
d) by first album do they mean first by date of issue, or first by passing the gold sales post?
If you're including stereo sales figures at all, a lot of the Columbia quads that were part of their initial quad release in January 1972 (Santana, Sly GH, Janis Joplin Pearl etc.) would be in contention too.
As fredblue said I did a post somewhere detailing some quad sales figures for some Columbia titles - they were reported in a couple of issues of Billboard in 1973 and 1975, but I don't think generally speaking quad sales figures were published anywhere. I've even heard it said that one of the (many) reasons for quad's demise was that (in the very pre-Soundscan days) that in terms of units sold quad and stereo sales were just tallied as one unit each, rather than by format. So as a result the labels had no way of knowing precisely how many quad copies they were selling, nor which areas were more 'quad friendly' than others and it just added to their general 'why are we bothering with this' malaise about the format as a whole.