The correct balanced equation is
You are correct. The balanced equation is
Both sides of the equation have 4 H atoms, 2 N atoms, 8 O atoms, and 1 Ca atom. You can replace the term atoms with moles.
The equation does have four coefficients. The coefficient for
It is not unusual for there to be mistakes in a textbook. New math textbooks are sometimes accompanied by an errata sheet. You should let your instructor know about this error.