BAT VK-51SE “Relative Volume” Adjustment?

Can someone please school me on exactly what the Relative Volume adjustment actually does on the BAT VK-51SE? Does it affect the actual gain of the unit? The thing I miss most about my previous preamp (Levinson 380S) is the subtlety and precision of the volume control. I’m mainly a late night Listener and the BAT’s volume even at 001 is a bit too loud.