Question: Among the users who are above 20, how many users use device model of ELIFE E7 Mini?
SQL: SELECT COUNT(T1.device_id) FROM gender_age AS T1 INNER JOIN phone_brand_device_model2 AS T2 ON T1.device_id = T2.device_id WHERE T2.device_model = 'ELIFE E7 Mini' AND T1.age > 20