Wrong number of results when filtering

Probably because you have a post with category1 too.

Check the categories here (site using wpsolr):
https://www.gotosolr.com/en/search-wpsolr/?wpsolr_q=solr

In your link, the addition of the results for each categories does not match the total of results displayed on the page.

It seems like (in my example) the number for category1 is just the addition of the categories under it, not including what’s in its own category. Only the categories that don’t have categories under it (in the results) are working.

I see your issue now:
https://www.gotosolr.com/en/search-wpsolr/?wpsolr_q=solr&wpsolr_sort=sort_by_relevancy_desc&wpsolr_fq%5B0%5D=categories%3ABlog

Blog category is selected, shows count 6, but 15 results are displayed.

After some tests, I decided to hide the count on top level facets, as the results are very confusing for a user.

Suppose:

post 1 -> category1
post 2 -> category2
post 3 -> category3

then results are:

If you selected nothing:

category1 (3)
> category2 (1)
> category3 (1)

but If you selected category1:

X category1 (1)

and If you selected category2:

category1 (1)
X category2 (1)
> category3 (1)

Done in WPSOLR 10.3