It's not the acts of all the apostles, it's the acts basically of Paul,and Paul's not considered an apostle by the guy who wrote the Acts of the Apostles.

它并不是所有使徒的传记，而是保罗的，但使徒行传的作者认为,保罗并不是使徒。

耶鲁公开课 - 新约课程节选

The titles of most of the books in the New Testament ; were not put there by their authors; they were put there by later Christian scribes.

新约所有篇章的标题,并不是作者自己起的;,而是后来基督教文士起的。

耶鲁公开课 - 新约课程节选