Fビザの滞在許可はDuration of Statusです
Jビザと同様、Fビザで入国した際に与えられる滞在期限はD/Sとなります。これはDuration of Statusを意味し、Fビザの場合はI-20が有効な限り滞在ができることを意味します。なおFビザの場合はGrace Periodが60日間ありますので、正確にはI-20の期限+60日が滞在期限となります。
9 FAM 402.5-5(L)(1)
a. An individual entering as an F-1 student or granted a change to that status is admitted or given an extension of stay for the duration of status. Duration of status means the time during which the student is pursuing a full course of study and any additional periods of authorized practical training, plus 60 days following completion of the course or practical training within which to depart. Since November 30, 1996, however, the duration of status of an F-1 student in a publicly funded secondary school cannot exceed an aggregate of 12 months schooling.