The AMOUNT/DRIVE (TIMING) knob sets the Threshold of the Compressor, and goes from 0 dB (fully counterclockwise) to - 40 dB Threshold (fully clockwise). The setting at 12 o'clock is - 20 dB Threshold.
The FREQ/RATIO (FEEDBACK/DEPTH) knob sets the Ratio of the Compressor in equal steps between these values: 1.0 - 1.12 - 1.25 - 1.4 - 1.6 - 1.8 - 2.0 - 2.5 - 3.2 - 4.0 - 5.6 - 8.0 - 16.0 - 32.0 - 64.0 - Infinite (from fully counterclockwise to fully clockwise).
Please note, that the values of the FREQ/RATIO knob, do not correspond to the lines printed on the frontpanel.
As for the remaining settings, the ATTACK and RELEASE are fixed at 10 ms and 200 ms, respectively.