Depending on your view, in the deck windows, next to where the track name, artist, played/remaining time and such show up, on the right hand side you will find three buttons:
SYNC
WIDE MASTER
If you click on WIDE once, it will change into +/-6%, next click 10%, then 16% and finally wide again.
Try setting it to 6% and see if that helps. Wide (default setting it seems) gives a 100% up and down margin. WAY too much for any fader, let alone the short ones on the RB. With the setting at 6 you should be able to get very close to the desired result I would think.
Let us know if that helps.