We decide how to change the dose based on how low the dose takes the cat. The high numbers are just bounces, or his body getting used to lower numbers again. Over time, as he gets used to normal blood sugar values, he won't bounce as much and will level out. There is no time frame for this, it is really up to each cat.
If you haven't seen the definition of a bounce yet:
Bouncing is simply a natural reaction to what the cat's system perceives as a BG value that is "too low". "Too low" is relative. If a cat is used to BGs in the 200's, 300's, or higher for a long time, then even a BG that drops to 150 can trigger a "bounce". Bouncing can also be triggered if the blood glucose drops too low and/or too fast.The pancreas, then the liver, release glucogon, glycogen and counter-regulatory hormones. The end result is a dumping of "sugar" into the bloodstream to save the cat from going hypoglycemic from a perceived low. The action is often referred to as "liver panic" or "panicky liver". *Usually*, a bounce will clear kitty's system within 3 days (6 cycles).
As you can see, you can get 1 cycle of nice numbers followed by up to six cycles of higher numbers. At least in the beginning. That also means it's important to try to get a second test each cycle, if you can, to try and spot those cycles with lower numbers in them.