May be these are the actual parameters?
Angle resolution: 0.1°
Angle accuracy: 0.5°
My Beall inclinometer has this spec: "The display always reads left to right, even if inverted, and a "hold" button keeps the measurement for reference. It has a range of 90° left or right and a resolution of 0.05° (accurate to 0.2°)."
I use the Beall angle gauge to set the blade (SawStop or Kapex), and then verify the cuts made on scraps. The Beall device has been so consistent in its accuracy and performance that I now trust it as much as I trust any other reference measuring tools I have, such as the Starett Combo Square or the Australian CNC machined square.
89.875* is more than square for all woodworking intents and purposes.