catpower1980: The Polish devs of Machinarium have published a graphics breaking down the sale of their indie classic "Machinarium". Apart from the 4 millions sales mentioned, it's only about various percentages:
http://www.gamasutra.com/blogs/JakubDvorsky/20160714/277049/Machinarium_Sales_Infographic.php

Spoiler: On the total amount of units sold, GOG ranks up at 2% (while Humble and Steam are at 35% and 26% respectively)