Problem sound level UR12!

I bought new one sound card UR12 usb and a pair of krk rp5 G3, but I have a problem of sound level.
When I puts reading mp3, or one reading composition in my daw cubase element 8, if I slow down the sound level completely on my UR12, me always hears the music weakly. :confused:
To agree you with me, that if I lower the sound level completely, I should hear nothing, just the silence!
Then, a person here had this problem, or a solution? :wink: