Measured Filter characteristic is half

I'm using ADAU1466, where is used coefficient calculations filter 2nd order.

When I test output/input signal with frequency analyzer, I measure only half dumping, like is set in block.

For example, when I set parametric filter, 1kHz, and slide dumping to -10, analyzer shows -5dB. Setting to -6, analyzer shows -3dB.

Simulated response in Sigma Studio shows right magnitude, but measured is half.