It's just 1/3 of those passages each day, so yest, 13 of them.
You do the second 1/3 after that, and the last 1/3 as a final review after finishing the whole book.
The first chapter is a pretty heavy load, so I think it would be ok to divide them up to two days, since later chapters are a bit lighter.
But you tend to have more stamina and will power early on, so you could just do them now too.
Don't think that the schedule is an absolute rule or something; you could change it as you see fit. Honestly the first chapters of TBR in my opinion was not that useful, since it covered way too much detail unnecessary for the MCAT.
