Why is the runtime 74 minutes?

FutureMeat said:
Every version of the movie I've found, both sub and dub, seem to have the runtime as 64 minutes. Wikipedia seems to list the runtime as 74 minutes, but also says "[The movie] is a special hour-long episode".

Wikipedia also states: " In the American dubbed version, the DVD features a second mini-feature in addition to the movie feature named The Uncut Story of Mewtwo's Origin. This 10-minute segment was originally part of Mewtwo Strikes Back's running length in the Japanese version, but it was cut from the U.S. release of that movie", which seems to imply that the 74 minute runtime comes from the American release, not the Japanese release.

If I'm wrong, then where do the other 10 minutes come from?