The H9000 input impedance is ~10kΩ bridging.

The DBFS lineup for line level (+4dB) is +26dBu ≈ 0dBFS.

The meters are set up to so that the red OVERLOAD LED will light if the signal ever hits 0dBFS.  The yellow LED lights up at -6 dBFS; green is at -60 dBFS.