High volume

Best bluesound, When I want to play music from my Synology Nas via the NAD C700 and I press play and the music starts playing, it does this at 100% volume. I'm afraid this isn't so good for my speakers. If I press - the sound immediately disappears and if I press + again the sound is immediately 100% again. What am I doing wrong. Do I need to change anything in the settings of the Bluos app or does it have to do with the software?