Because that’s the way procedures work. If you are cooking bread (a recipe is just a procedure), you don’t say that it only takes about total 20 minutes to make the bread. You have to measure the ingredients (takes time), mix them (takes time), let the bread proof (takes lots of time), knock it down and maybe proof a second time, and finally bake it for that 20 minutes. You include all the time of the procedure when describing it. You may be doing other things during some of the steps but that doesn’t mean that you leave out the long periods when you are letting something just sit.

I’ve developed lots of procedures as part of my work. I have to provide details on the procedure and, often, tell someone how many hours the procedure will take so that they can budget both my time and other people’s time to do the procedure. One of the procedures I have developed only takes about 5 minute to prepare and measure the results at the end but there is a 2 hour wait time in the middle for the reaction to go to completion. That 2 hours has to be figured into the budgeting of someone’s time. The procedure takes 2 hours and about 5 minutes, not 5 minutes.