You'll do better selling 2,000 books at a discount through major distribution channels than you would selling 200 at list price on your own. (ingramspark.com)
The third major distribution channel besides Amazon / Kindle and Smashwords is Google Play, but it has the disadvantages of a reportedly clunky interface, and the right to set its own sale price for your books. (hyperedits.com)
So likely, subscription does not fall into it, but e-book sales by the publishers were recorded by Amazon, Barnes and Noble, Kobo and all other major distribution channels. (goodereader.com)