The G (academic elective) requirement can be fulfilled by courses in the A-F lists beyond the minimums, or by courses designated as academic electives but not in the A-F lists.
The math and foreign language requirements allow for validation of lower level courses by completing higher level courses. For example, completion of Spanish year 3 validates Spanish years 1 and 2, even if they are absent from the high school record (e.g. because they were taken in elementary or middle school, or because the student is a heritage speaker who started in Spanish year 3). In math, algebra 2 validates algebra 1, and precalculus or higher math validates algebra 1 and algebra 2.