ADM3053

As testing, ADM3053 pin7 GND1 input impedance(about 20ohm) is different than other GND1 pin(about 2ohm).

When I let pin7 floating, the single noise is less then connected GND1.

Can you let me know why pin7 is different than other GND1 pin.

if I let pin7 floating, is it OK?

thanks.