It is closer to 1/3 (sometimes closer to 1/2) than 1/4 for the percentage of courses or credits that a typical liberal arts major consumes out of the total courses or credits. However, the main issue can be the lengths of the prerequisite sequences for required and elective courses in the major, if the student is forced to graduate in a smaller number semesters due to bringing in lots of AP credit that is not applicable to his/her major.