Can someone explain TfL's 18+ Student Travel discounts to me please?

[neemcheenge]

We live in zone 6 and, later this year, DS is likely to be going to university in zone 1, travelling by rail, tube and/or bus.

I've been looking at this TfL page about 18+ student travel discounts: tfl.gov.uk/fares/free-and-discounted-travel/18-plus-student-oyster-photocard. I think it means he will get a 30% discount on the full adult fare, yes?

However it also says that if he adds a 16-25 Railcard he will get a 34% discount. Does that mean an additional 34% discount on the already- reduced-by-30% fare?

Hopeful bump?

No, it’s either or.

Ok, thanks that's not at all clear from the info. So is it true to say that the TfL discount is slightly less, but applies to bus/train/tube, whereas the Railcard discount applies only to rail?

My daughter informs me that the discount applies to tube and bus as well as train.