What does a solid blue status light mean?

A solid blue status light indicates that treatment is in progress.

When a treatment session is complete, the blue status light will change to green and the device beep as follows: beep-beep-beep ... beep-beep-beep ... beep-beep-beep

If you pause a treatment mid-session, the blue status light will start to blink and the device will start a slow, repeating beep.