The Enforcement Rules of the Motion Picture Act Article 11

Advertisements shall run for no more than twelve minutes for every film screening.Advertisements as used here refer to film advertisements as well as other advertisements and slides of a non-promotional nature.Where advertisements as mentioned in the first Paragraph exceed nine minutes in length, the remaining allotted time for advertisements must consist only of film advertisements.In addition, at least one film advertisement shall be for a domestically produced motion picture.
中文原文 電影法施行細則第11條
電影片映演業映演廣告片時間,合計每場不得超過十二分鐘。
前項廣告片指電影片之廣告片及非宣傳電影片之廣告片、幻燈片。
第一項映演廣告片時間逾九分鐘者,其映演電影片之廣告片時間不得少於所逾時間,且國產電影片之廣告片映演數量不得少於一部。

English translation for reference only; the Chinese text prevails. Not legal advice.