For English-translated doujinshi: "Extra Quality" means:
: The series focuses on the psychological and physical breakdown of Tsubaki, as her initial disgust and resistance slowly give way to involuntary obedience. Media Adaptations and Availability maid kyouiku botsuraku kizoku rurikawa tsubaki extra quality
To illustrate the standard, here is a short, original scene written in the extra quality mode: here is a short