There's actually three values, the first being volume. The percentage in the STARTS setting determines where you want AOA audio alerts to begin beeping. It continues beeping faster as your AOA increases, until it turns into a continuous sound at the SOLID setting. The percentage numbers correspond to locations/colors on the AOA indicator. It's up to you to decide where you want it to start beeping, and where you want it to become a solid tone. These are audio settings only, and have nothing to do with the actual calibration of your AOA.
Installation Guide (revision AN) page 4-21
Pilots Guide (revision L) page 12-19