Indian publishing claims to have a magic number—10,000.
The sale of 10,000 copies makes a book a bestseller. Publishers are happy, and subsequently, so are authors. Bigger things follow this number: multiple reprints, a push for a film deal, talks about a sequel, etc.
Oddly, this magic number strictly adheres to the number of physical copies sold. This is odd because India has finally thrown a publishing googly that could very well change the game.