I believe this is a difference in IDs added (first instance) vs. observations with that ID and identifier (second instance). That user has added 83 IDs of that taxon, but only 67 observations identified by that user have the ID of that species (presumably because some IDs are disagreements and the observations are a higher level taxon).
See this post:
https://forum.inaturalist.org/t/only-1-identifier-for-species-but-top-identifier-is-someone-else/11177
And this related feature request:
https://forum.inaturalist.org/t/only-1-identifier-for-species-but-top-identifier-is-someone-else/11177