This Wordpress plugin is an add-on for the FacetWP plugin (https://facetwp.com/). It adds a new facet type called "Yearly Archive" which can display a list of years with an associated counter of published posts.
The counter marks a larger number than the number of posts actually published.
This is because your FacetWP plugin is indexing both posts, pages or some other Custom Post Type. You should use the facetwp_query_args Wordpress filter to make it index only the post types you prefer.