Recovery week question

There was a training plan discussed a little while back that had a 4-week progressive training, then 1 week recovery, then 4 week progressive training, 1 week recovery, etc, etc.

The 4 weeks were described as:

Level 1
Level 2
Level 3
Level 4
Rest
Level 2
Level 3
Level 4
Level 5
rest
and so on and so forth...

My question is during the rest week, how much do you back off. Do you go back to week 1 (level 1) mileage, etc or do similar workouts as say your level 4, but just not as many (more rest days).

Thanks to all in advance who respond.