If a website's search engine saturation with respect to a particular search engine is 20%, what does it mean?

Q) If a website's search engine saturation with respect to a particular search engine is 20%, what does it mean?

Answers:
• 20% of the webpages of the website have been indexed by the search engine
• Only 20% of the pages of the website will be indexed by the search engine
• 20% of the websites pages will never be indexed
• The website ranks in the first 20% of all websites indexed by the search engine for its most important search terms