The number of indexed pages jumps a lot. How right?

Question

Google

Site https://1ya.ru (commodity-analytical aggregator, tracks prices, demand, etc., these are not just duplicate pages, but also content that is useful for the user). Although Google will probably not like 80% of these pages.
The problem is that if you look at all indexed pages, i.e. look for "site:1ya.ru" then every day the issue jumps from 30 thousand to 200 thousand. What to believe?
Everything is complicated by the fact that if I want to see what is indexed within https://1ya.ru/goods/ (only product pages) through "site:1ya.ru/goods", then millions of pages periodically appear there.
How to check the correct number of pages in the index?

Answer 1

Through google search console is the most correct.
In the same place, you can track this page file into directories through sitemap.xml in more detail.