RobotC Encoder

I have one question – if optical shaft encoder has 90 slots inside – which means 90 ticks will be one revolution. Why in RobotC, for SensorValue] = some number, we use number/360 to calculate the rotation?

Well it has to do with how the quadrature encoders work. There are 2 little light sensors and this makes 4 unique states that cross 1 at a time through the notch.

high high
high low
low low
low high
Each of these states is read as a single tick making a total of 360 ticks per rotation.