HI does mean it's very high. Please try to get some spot checks today. You may find as I did that the N just doesn't last long enough.
3.5 or even 2U could still be too high or too low of a dose.
If you could check at +2 (2 hours after you gave the shot) and again at +4 or even +3 and +5, you may find the dose knocks your kitty's blood sugar low, like maybe drops it by 200 - 300 points, or it may not move the blood sugar at all.
Let's say it drops the blood sugar to 150 at 2 hours after the shot, then we know the dose is too high because extreme swings in blood sugar, in my experience only, causes Tucker to feel crappy. If at +2 the meter reads 400 then the dose may need adjusting also. But... all of this really depends on you being your cat's advocate and collecting data, hometest and keep hometesting until you see how the kitty is reacting to the insulin. I mentioned this on the other thread,for Tucker the N did not last long, he metabolized it too quickly and spent most of his days going up and down like a roller coaster.
A switch to Lantus, Levemir, PZI or I believe a new insulin called ProZinc should be looked at.
Great job testing the BG this morning.