You really want to see some tests in the +3-+7 time with Vetsulin because that is when it will be working the most. Increasing dose of Vetsulin based off of only a preshot number can be dangerous because it will be when there is no insulin on board and will likely be the highest number in the cycle. You could end up with low numbers at the peek of the insulin causing higher numbers at preshot times causing increases in dose, causing all of that to get worse. That kind of cycle almost killed my Cecil before I started talking to the shelter manager and figured out what was happening to him. He got too low and they ended up taking him to the vet earlier in the day because he was just laying in his kennel, that's when the lower numbers were spotted and I could tell what was happening and suggested more testing, getting him onto a different insulin, and into foster.
Vetsulin and Caninsulin are the same. The manufacture changed the marketing name in the US to Vetsulin when they brought it back to the market after it was pulled for a while. They still market it as Caninsulin in other countries.
As for the difference in numbers. The higher the number, the bigger variance you will see. As you get down into the better numbers, they will get closer. Even though 425 and 324 seem like a long ways apart, it doesn't really matter because they are both high your dose adjustment should be the same.