However, this is not the only way to measure freshness. Search engines may learn how frequently pages change or use other methods to improve freshness to maximize a smaller crawling capacity. Numbers may also be overstated. There are various reasons why this occurs. It takes longer for them to return and gather non-submitted pages.
Freshness shows the age of listings, from best to worse case scenarios for each search engine.
Ideally, a search engine will find your pages as it follows links while crawling the web. Realistically, your pages will appear much faster if you submit them directly to the engine. This shows how soon to expect a page you submitted to appear in the search engine's listings. Once a page has been submitted, a search engine will usually find other pages from the site by following links from the submitted page. Depth TThis is closely related to non-submitted pages.