Phono stage gain too high??? Should I return it??

Just purchased a used ARC PH-7 and am wondering if it is defective as the gain seems awfully high.  I have it running into an ARC LS-27, and it's fed by a Project RPM10 with Sumiko BlackBird Hi Output (2.5mV output, 47K ohm).  I was expecting it to be the lowest gain input in my system, but it's so loud, I cannot set the LS-27 anything over 7/8 (my digital input, Schiit Bifrost is in the 12-16 range), and it does not go soft enough for late night listening.  

The only way I can get it to a reasonable gain level is to set the load at the lowest setting (100 ohms), which totally squashes the dynamic range.

The seller gave me a 30-day return window.  I really like the PH-7 in terms of tone, but is something wrong with it??  It's rated at 57.5 db gain which is modest by most standards, I think.  I have other phono stages rated at 60+ db and in my system, they exhibit LESS gain.  How is this possible??