How many credits have been displayed from episode 1 until 10?
credit displayed refers to credited = 'true'; from episode 1 until 10 refers to episode > = 1 AND episode < = 10
SELECT COUNT(T1.person_id) FROM Credit AS T1 INNER JOIN Episode AS T2 ON T1.episode_id = T2.episode_id WHERE T1.credited = 'true' AND T2.episode BETWEEN 1 AND 10