Some people have a 6day Keto/ 1 day off plan... personally I dont think it matters when the carb up day is, but that depends on how long your body takes to get into Ketosis. My theory is that its 6 days Keto, because it takes most first timers on the CKD a few days to get into KETO, and by having the CArb up on the 6th day it ensures that you have atleast entered Keto. The amount of time to enter Keto should decrease after carb up days the longer you are on the diet and the more strict you are at having carbs closer to 0. I try to push that my only carbs come from Metamucil (1.6 carbs per teaspoon) for fiber, and just trace amounts in anything else. I reccomend reading the Mr X manual on CKD, and doing a search on CKD and reading through some of the older longer posts on the subject.