This type of ticket issued If you need a break journey. Like I want to go first Puri then Howrah and 12802 Purushottam Exp does not go Howrah directly, so they calculated 1859 km + 500 kms = 2360 kms SF Express ticket Value which might be Rs 855/- (including SF charge & reservation fee) instead of Rs 1090 (Rs 750 + Rs 340 (12838 Puri HWh Exp- 2nd lap). In addition i have to pay Rs 20 extra for 2nd reservation fee for next connecting train.
Hope I make you understand.