Your message is a little garbled due to initially saying railcard rather than ticket, then the first paragraph doesn't mention London at all, then your last one asks if it is valid to London.
However, if I've understood you correctly you had intended to buy a ticket for a colleague to travel...
No doubt boosted by the salary savings from employing insufficient train crew numbers to run a reliable service and cover adequately for disruption, sickness, training days etc
Well, as I understand it, it comes from the railways own internal reporting systems - about the only place info that detailed could come from - but in a simplified format. So there could be a few things going on to cause minor discrepancies - 1) how well the railway system is tuned into...
For cancelled trains, the 30 minutes refers to the difference between the timetabled arrival time at the station you leave at, compared to the actual arrival time of the train you end up getting instead. Looking at Realtime trains and assuming you were going all the way to Brighton, the 1800 was...