I agree with Tom. The beauty of the Barry P plan is that you don't really have to think about your running. It's either
"I ran easy yesterday, so today is one the three longer runs."
or
"Yesterday was one of the three longer runs so today is easy or a rest."
Because you get an easy day after every longer run, and nothing is too long you should always be good to go again by your next run, so pay more attention to how they fit with your other sessions.
In terms of distance, I think of the total week's distance and use that. If I want 30 miles in a week that will be 3 runs of 3 miles, 2 runs of 6 miles, and 1 run of 9 miles (Divide the total week's miles by 10 - that will be your recovery run. Double that distance, it will be your mid length run repeated twice, treble that distance and that will be your long run).
"I ran easy yesterday, so today is one the three longer runs."
or
"Yesterday was one of the three longer runs so today is easy or a rest."
Because you get an easy day after every longer run, and nothing is too long you should always be good to go again by your next run, so pay more attention to how they fit with your other sessions.
In terms of distance, I think of the total week's distance and use that. If I want 30 miles in a week that will be 3 runs of 3 miles, 2 runs of 6 miles, and 1 run of 9 miles (Divide the total week's miles by 10 - that will be your recovery run. Double that distance, it will be your mid length run repeated twice, treble that distance and that will be your long run).