Hi and welcome to PZI.
My cat Henry gets a different reaction than a lot of cats here to his insulin and has a different dosing schedule than normal 12/12 hour dosing because he is always lower for his PMPS than AMPS. I really can't advise you about whether its a bounce or not, but it doesn't really seem like it to me. If he had no insulin last night it may have allowed him to stay higher today. Some of the the members who are experienced and give others advice are on right now, so maybe they will check in.
Just wanted to welcome you!
Angela