Well, look at it this way also, though.
"A" single has four A-Sides, but it sold 1.5 million copies or so.
But dividing that between A-Sides, thats pretty much only 375,000 or so copies per song.
Now look at HEAVEN, which had 2 A-Sides, and had total sales (physically+digitally) of nearly 2 million. Divide it up, and it's 1.0 million copies per song.
I'm not saying this is how it works, but it's a way of looknig at it.
Some people will be like, to a triple a side, they will say the title track is a more popular song whatever week than a single a-side single, even though the sales are near ever.
its like ... for example
1. 3 A-Side (110,000 copies sold)
2. 1 A-Side (100,000 copies sold)
It's probably a more powerful/popular song, since it got 100,000 on its own rather than getting 110,000 with the help of two other songs.
see what I mean?