How many people were not credited at the end of the "Admissions" episode?
not credited refers to credited = ''; the "Admissions" episode refers to title = 'Admissions'
SELECT COUNT(T2.person_id) FROM Episode AS T1 INNER JOIN Credit AS T2 ON T1.episode_id = T2.episode_id WHERE T1.title = 'Admissions' AND T2.credited = 'false'