"Analog Encoder" counts the overflows in both directions, so you can servo multiple rotations. This is explained in section 16.11 in the Talon SRX Software Reference Manual. Also in section 17.3
If you want your position to be [0 to 1023] and not track overflows, you can select "analog potentiometer" (section 17.2), however unless you can guarantee your mechanism can't turn more than one rotation, this is likely not what you want. For example if you have a PIDF control loop and you are serving to a position, and the mechanism overshoots your MA3 encoder, you would want your control loop to servo back gracefully, instead of seeing a major discontinuity of 1023 => 0.
The 2015 implementation uses Talon SRX raw units for sensor, see section 17 for the details. It's not in degrees.
Documents...
http://www.ctr-electronics.com/talon...ical_resources