Formula of the gain value for ADV7441A

Hi Expert,

Please tell us the method of calculation for the gain value at below condition.
【Condition】
AGC: Off
DIGITAL FINE CLAMP: ON
Input signal: 1Vpp = amplitude voltage of Sync on Green video

It seems that the value becomes considerably low at gain = 1.
Could you provide us the any information for that?

Best regards,

RYUJI