Audio ducking duration

Is the duration parameter broken? If i set up a ducking system: I throw a grenade and i want background music to duck. It is ducking fine, but it ducks throughout the entire duration of the grenade cue. I want to be able to control the ducking duration seperate from cue length. No matter what value I type into the field “duration”, the ducking effect is applied for the totalt amount of the cue length. Thanks