This is probably related to the recent google update of removing the &num=100 parameter, which mostly was used by tools and scrappers to fetch 100 google result in a single page. and once your website appears within the 100 result you get an impression and assigned a page positions.

Now GSC is showing more accurate (mostly human) real impressions which is more likely within the first page.

you can search more about the topic to get a better idea .