Stereo Tool Preset Fixed !full! Link

: Fixes phase issues that can cause audio to sound "hollow" or disappear when played in mono. AGC (Automatic Gain Control)

Thus, a refers to a modified version of an original preset that has been calibrated to work reliably regardless of the source material, or specifically tuned to your hardware.

If you are looking to "fix" or lock in your settings so they don't shift when testing different sounds, here is how you can manage that workflow: 1. Lock Audio Settings While Changing Presets Stereo Tool

to fix phasing errors in old recordings and adjustable stereo widening. Top Presets and User Recommendations