His nadirs might vary. That's normal. Some cats are consistent with a nadir at a particular time unless there is a bounce or New Dose Wonkiness, some cats have nadirs that move.
What can help is to look at the change from one test to the next and see how fast the cat is dropping. It looks to me like Sampson might be clearing a bounce tonight, although sometimes cats will bobble around while they are still in a bounce. You'll know if he's clearing it if he continues to go down until he (probably) hits green again. Bounce cycles override normal cycles.
The drops will improve when he doesn't go so high. The goal with feeding is to ANTICIPATE the drops, or catch them at the first sign, and feed then. Feeding after the cat's dropped 100 points in an hour or two is too late to prevent the next bounce in most cats. There is a good thread on "Feeding the Curve" in the thread I've linked below, look in the second half of the first post.
Yes, a tightly regulated cat will have more of a line than a curve - they might only vary 10 points in the entire day.
It's good to read in advance on shooting low, ie shooting the full dose into normal numbers, before you are faced with it. Take a look at the
Where Can I Find? post - the three things that relate to shooting low when faced with a normal preshot:
1. Sticky on Shooting and Handling Low Numbers - look at becoming data ready & handling low preshots
2. Shooting low (second half of the post)
3. Tight Regulation Protocol, Myths Debunked - look at the post on shooting a dropping number
Take the time to look at the spreadsheets that are linked in the second thread. It really helps to see the actual change after shooting a lower preshot.