Max Angular Speed (deg/s) - turn rate. I'm still not 100% sure what's the reference, but you can figure it out by comparing it to other ships, especially ones within the same class. The higher the number the faster the ship turns.

Time to 90% Max Angular Speed (s) - this is what we call responsiveness. How sluggish a ship is to change of direction. Since it's measured in seconds, the smaller the number the more responsive a ship will be. This is evident by looking at the Saishi which has the lowest number out of any snub is the most responsive snub in the game while the Camara which has the biggest one is the least responsive. Responsiveness is only worth comparing within the same class as it's much less impactful than the turn rate globally (battleships might seem super responsive compared to fighters, but that's to compensate for their ridiculously low turn rate. If you look at it closely, you'll see battleships don't have a problem with sudden change of direction, although the change itself will be hard to notice because of the low turn rate).