I received a rejection mail at 02:15am IST and then an acceptance mail (saying I should've received it in the first place) around 2 hours later for the 'advisor

I received a rejection mail at 02:15am IST and then an acceptance mail (saying I should've received it in the first place) around 2 hours later for the 'advisor track'. Making me wonder how many tracks are there? And what's the difference between them? There seems to be no mention about the track in this blog post.