Delay Repay miscalculated... yet again! What's going on?

Once again, Delay Repay have stiffed me. For the 5th time this year SWR seem to be incapable of calculating that a cancelled train on a line that operates one train every half hour is not a 15-29 minute delay but a 30 minute delay. I'm sick of having to appeal my claims and I'd love to know what timetable they get their figures from! Personally I use the South Western Railways very own Mobile App...

...and when that doesn't work (which seems to be happening more and more) I use National Rail Enquiries...

...and sometimes I've even been known to use an online independent timetable...

SWR really need to sort this out as it's annoying me, costing me money and makes SWR look like a bunch of incompetent morons.

Having complained about this TWICE and receiving no reply, I'll be escalating this problem with the Rail Ombudsman.