OK Duncan,
Firstly, I do not work for TfL. All the information I display comes from data supplied by them. Secondly, as I said in my original reply, I do not want to major on maximum fares. No-one should be aiming to make use of them and it could be very costly if they do.
It’s possible that London North Western Railway haven’t changed all the Watford Junction fares. They have history for making some changes at the second fares revision of the year.
The maximum fares for SE High Speed will be the same as the single prices.