The total number of URLs that appear in the Google Core Web Vitals report in the Google Search Console is not important. Rather, it depends on the number and type of errors reported.
The Google Core Web Vitals report on Google Search Console can be confusing in a number of ways. The errors and suggestions for improvement reported there are based on real user data. So you are not measured by Google. As a result, changes in the report will only show up around 28 days after improvement measures have been implemented on a website.
The fluctuating number of URLs that appear in the Core Web Vitals report can also be irritating. But you shouldn’t let that distract you. John Mueller said in the Google Search Central SEO Office Hours on April 23 , the size of the sample of URLs for the report could change. That is not a cause for concern. It is more important to focus on the number and type of problems reported.
The same applies to the report on mobile friendliness in the Google Search Console: Here, too, the number of URLs displayed can fluctuate , which is not a cause for concern as long as the number of reported errors does not increase.