That is because of slack, my friend.
02561 should have departed at right time from Aligarh but it was looped (even though running right time!!!) nd made to wait for 02815 which was still 15-20km away from Aligarh. If 02815 didn't have halt at Aligarh. Then this Overtake can be justified. But both trains having a scheduled halt at a station and one was looped despite being on time!!!!