There are 16 ac3 coaches (as mentioned in this site) and each has 72 seats as it is lhb rake, so 16*72 = 1152 seats
occupied seats= 1152-251 = 901 out of 1152 i.e. 78.21 % as i said almost 80%. Reverify your facts and then make statements. Also according to the picture attached below, it has pretty good occupancy for a full 3ac train that too with dynamic pricing.