Hi Laura,
I’ve worked out a possible scenario that works. Did you possibly touch in at Hayes, decide to get a coffee, then touch in again more than 2 minutes after the first one? If you did then it looks like this:
Hayes – Hayes £0.00
Incomplete journey at London Bridge NR £8.60 (it’s now after 6.30 so peak)
London Bridge – White City £3.00
White City – Oxford Circus £2.50
Oxford Circus – London Bridge £1.90 (reached zone 1-2 cap of £7.40 excluding the incomplete journey)
London Bridge – Hayes £2.70 (charged as a zone 3-5 extension fare as you’d capped for 1-2)
Total £18.70.