From the documentation for fints: "If there are duplicate dates and times, the fints constructor sorts the dates and times and chooses the first instance of the duplicate dates and times. The other duplicate dates and times are removed from the object along with their corresponding data." So I suspect you have 100 duplicate dates.
Consider storing your data in a timetable instead of a fints object as the warning at the top of that documentation page recommends. You can have duplicate time and date data in a timetable:
>> T = datetime('today');
>> v = [0; 1; 2; 0; 2; 3];
>> tt = timetable(T+v, v.^2)
>> unique(tt.Time) % only 4 unique times
>> height(tt) % 6 rows in the timetable
