Let me jump in and see if I can help with some of the confusion. Apologies if I make it worse!!
A cat that is "regulated" is a kitty that is spending most of the time in normal or close to normal numbers -- or at least below renal threshold (i.e., below about 220 on a human meter). A cat that's tightly regulated is, as Elise noted, spending time in the 50 - 120 range. So, when you say you want Cotton to be in regulated numbers, I think you're referring to a different range than how we use the term.
Whether you choose fo follow TR or SLGS, ultimately you want to want to be shooting progressively lower numbers. Everyone is apprehensive about shooting low. It can be scary. No one would expect you to shoot low numbers from day 1. Think about where your comfort level is and then as you gain confidence and know how your cat responds to Lantus, aim to shoot lower numbers in a step-by-step way. Most people make the assumption that if you were to shoot low, your cat's numbers would bottom out. That's likely true with Caninsulin. It's not typically the case with Lantus. Because Lantus is a depot insulin and isn't as potent at Caninsulin or Novolin, we rarely see numbers that we can't steer with food if you shoot low. I would shoot any number over 50. I'm sure that sounds terrifying to you! What may help is to understand that the ideal Lantus cycle is flat. Take a look at
Max's spreadsheet. Elise would routinely shoot low numbers and what you see are very pretty flat cycles. The basic mantra with Lantus is "shoot low to stay low." If you look at the sticky on shooting and handling low numbers, while it primarily applies to TR, there's also a section on being data ready. You want to be able to know when onset and nadir fall in order to tackle shooting lower numbers. Cotton hasn't been on Lantus long enough for you to have accumulated that knowledge.
I also agree with Elise that having more PM cycle tests would help you to get a better handle on how Cotton is responding to Lantus. It's not uncommon for a cat that's switched insulin to have a marked initial response. That's likely where that blue number came from. It's going to take 5 - 7 days for the Lantus depot to form and stabilize. That doesn't mean you get a pass, though. Many cats like to spend time in lower numbers at night. Getting a before bed test every night will help you go to sleep knowing that your cat is in safe numbers. In addition, if you don't test at night, you may miss a dose reduction and, just as importantly, you're missing half of your data. (If it's not obvious, we're pretty numbers obsessed.)