Hi kosss1977,
Good question.
At the moment the compression quality is set to the default of 80%. I found this gives the best results. In a future version they will be the ability to change it. But to save confusion and any rubbish images I have stuck to it. If you are confident about changing the value directly please open PLUGINS/mediawebp/classes/class-admin.php. Ln 266 and change it to
imagewebp( self::$_img, $filearray[‘file’] . ‘.webp’, NEW_QUALITY_VALUE );
e.g for 60% quality
imagewebp( self::$_img, $filearray[‘file’] . ‘.webp’, 60 );
Hope that helps ??
Steve