On https://musicbrainz.org/user/reosarevok/collections there is a count of added entities to the collection.
But there should also be a count on the actual collection page like https://musicbrainz.org/collection/2d5b6052-9f4b-49c1-8e86-2c83cdc3b6e3/

Something like "there is/are # $entity(es) in this collection"