Compensation value. I just can't be bothered for less to be honest.
Most of my claims are under a fiver but they add up:
2022-02-06 £3.52 for 15-29 minutes due to delay on a Bournemouth - Woking train causing missed connection, catching the train half an hour afterwards
2021-12-18 £3.90 for 30-59 minutes due to Southern service cancellation
2021-11-14 £5.95 for 60-119 minutes due to failure to call by an SWR replacement bus from Bournemouth - Eastleigh hence missed connection on the only direct train in the morning to Farnborough, and the timetable is written a way that 30 minutes late into Eastleigh will result in 80 minutes delay due to additional change at Basingstoke into a slow service
2021-09-24 £27.83 for 60-119 minutes due to signalling fault affecting an XC train from Bournemouth - Birmingham
2021-05-27 £2 for 15-29 minutes due to delay on Brighton - Southampton service, in addition to confusing signage at Southampton resulting in a missed connection
For a 15-minute delay, the ticket value needs to be over £40 return to reach £5 compensation, and for a 30-minute delay, £20 return. For people live south of London not on the Thameslink line, it's unusual to have an off-peak return journey over £40 without crossing London, when all the fare saving tools such as railcards and split ticketing are used, and once a journey involve crossing London on a flexible ticket basically there won't be any hope of getting delay repay for the whole journey because of the "generous" allowance given, that in practice catching the train half an hour before the itinerary is commonplace.
If you don't claim when the compensation value is under a fiver, I think you will have already given up many delay repays for delays under an hour.