Nudge Automation down 1 Step
Moves the selected automation curve down by 1 step. A step is dependent on the type of automation. Volume is stepped in .1 dB increments.
Overview of automation in Logic Pro — Apple Support
Automation refers to recording, editing, and playing back the movements of faders, knobs, and switches. Using automation, you can create changes over time to volume, pan, and other settings. You can add automation to all track types.