Q32, please, help me to find a mistake

Plese, look at my solution. To me everything seems simple, however, the result is different. Maybe I made a mistake?

WITH rental_inventory AS (
  SELECT 
  R.inventory_id,
  I.film_id
    FROM 
      rental R INNER JOIN inventory I ON R.inventory_id = I.inventory_id 
    WHERE
      DATE(rental_ts) >= '2020-02-01' AND DATE(rental_ts) <= '2020-02-29'
)
SELECT 
   count(*) 
FROM  
   film F LEFT JOIN rental_inventory RI ON F.film_id = RI.inventory_id
WHERE 
  RI.inventory_id is null