Here is John Mueller from Google explaining .
Google has published a beginner/starting seo video around what metrics Google has to be had to measure your index rely in Google, i.e. the quantity of pages Google indexed from your web web page. As you all realize, there are 3 number one methods to do that, together with the website online command, the search Console index fame document and the Sitemap record.
It you need help under standing why your pages are not index properly contact me today and I can help.