A person can have more than one middle name.
Often a person (like George W. Bush) chooses to use just an initial, W., to distinguish himself from his father, or simply because he likes the sound of it. Some people initialise their first names - J. Edgar Hoover. This often means they are called by their middle name as a first name.
You can be called Peter A.B.C. Smith if your parents christen you Peter Alfred Barry Charles Smith. But that's not common except in royal circles.
Student or Learner