That takes nine to 10 hours. Some people take the guesswork completely out of the equation by having a coach tell them how far to run each day. Just look at the schedule, then go out and do it. I suppose if you have bought into the belief that a coach absolutely knows what is best for you, then in your own mind you will make that designated mileage the right mileage. I never was able to fully embrace that strategy, probably because I'm far too independent and skeptical to believe someone else knows what is best for my running.
Some people run the same mileage every day.
That too is a strategy that I could not adopt. Conversely, there are days when nothing is working right. Bagging the run early is not a good habit to develop, but seems an appropriate action on those horrific days. You sure aren't going to get any extra credit for pushing yourself through a terrible run, unless it is from yourself. And you probably aren't doing your body any favors, either.