Reading comprehension is a skill. If UCI class size is 104, then by 3/15, UCI must have offered admission to, at minimum, 104 students. Obviously, not all 104 students will attend UCI. For 104 spots, assume they will offer admission to ~250 students in total? (2.5 X seems to be a reasonable multiplier for most schools).
To your original question, it is theoretically possible that UCI has offered admission to 104 out of an eventual 250 students. Thats only 40 percent of admission offers made.
So, based on the AAMC rule quoted, at this point in time, UCI could have tendered anywhere between 40% and 100% of their admissions offers by 3/15 --- info that is completely and totally irrelevant to any applicant.