hi elizabeth!
One of the things we look at is how many points per hour a cat is dropping. When you check her preshot, say last night's 397 and then the +2 with a 255, that's a drop of 142 points in 2 hrs, or 71 per hour. That's pretty significant, especially for that early in the cycle. We don't know yet when Mary Grace's nadir might typically be, but many cats nadir is somewhere around 5-7 hrs after their shot. If Mary Grace kept up that rate for another 3 hrs, that would've been another drop of 213 at +5, with a resulting BG of 42.
Some cats hit their nadir between +2 and +3, but many are later in the cycle.
You might want to do the math when you get a +2, figuring out the number of BG points dropped per hour to help you figure out when to test next. it's too bad cats don't have a continuous monitor, isn't it?! that would be so great! cat_pet_icon
hope you're having a great week!