To clarify, the combination of subwoofer trim (in Channel Calibration menu) and two channel subwoofer offset (in Surround Configuration menu) should not exceed 15dB of attenuation. Once those two levels request more than 15dB of attenuation, the sub calibration tone jumps in volume.

Quite frankly, if you need to trim your sub level down by more than 15dB you should alternatively reduce the gain on your subwoofer amplifier.

Best,

Scott