Work speed

In Chapter 4, page 37, the book says, “On average, an experienced copyeditor can edit about five pages of double-spaced text an hour.” As Pat also mentioned in class, this speed is the case for a full-fledged copyeditor. Then what is the work speed that a beginning copyeditor should aim for? Is there a standard speed that the copyediting profession demands or expects of a beginning copyeditor?