Thats pretty impressive IMO, if your comparing 300k to his last album (I believe it did something crazy like 790k) or even any of his other projects. Since 2014 the whole sales of music has completely changed. Not many people buy physical copies anymore, even less buy albums off of platforms like iTunes and more people are streaming and/or downloading illegally. Combine this with the fact it leaked a few days before it was supposed to drop.
If you compare Em's 300k to other rappers that dropped this year, Kendrick did 600k and hes one of the most pronounced rappers in the game, Drake's more life only did 500k and hes pretty much the king of sales/streams as far as rap and male artists. Also Logic did something like 300k as well, either way these numbers are pretty good, also dont forget he pretty much told all his fans that were trump supporters to fuck off aha.