Times in a "normal" process include "crossover", so for 3:15; pour the developer in with the tank rotating and start the clock then dump the tank at about 3:00. Development actually continues. At 3:15 pour in the bleach. The bleach stops the development and does the rest of it's work.
The only time that is target critical is the developer time. The rest of the chems "go to completion" so extra time, like doubling or tripling, has no real penalty and is cheap insurance with reused chems, and without replenishment.