When conducting competitor analysis, we use "site" command to get the indexed page number from a certain domain or a certain site.
But it seems that I cannot get the correct(or precise) number.
"site:sample.com", I get about 10000 results.
"site:a.sample.com" I get about 20000 results.
"a.sample.com" is a subset of "sample.com", i.e., the indexed page number of "site:a.sample.com" should be less than the indexed page number of "site:sample.com".
Do I misuse the "site" command?
Are there any other better solutions to get correct(or precise) indexed page number from a certain domain or a certain site?
Some people said that google search does not display all the indexed page results. Refer to this article: Why the number of indexed pages decreased for a “site:” search
Are there any official articles about this subject?