The learning level of American college students is measured by "credits". One credit means that students attend classes for one hour every week throughout the semester, so the credit is also called "one credit hour". In order to get a degree, students must accumulate certain credits and complete a certain number of courses stipulated by the selected major. The credits obtained by different courses are different, which generally depends on the number of hours in this course. Schools usually have regulations on the upper limit of the number of students who can study and the lower limit of the number of students who must study.

60 credits is equivalent to 30 credits per semester, that is, in a semester, there are 30 hours of classes per week and 6 hours of classes per day. This is quite difficult. For every hour of class in a university, it usually takes 2-3 hours to review and digest. Coupled with the language barrier, it is difficult for even very diligent and smart people.