Why has my tube journey cost 10p?

[1lifeliveitright]

Just got tube from King's Cross to Victoria as an adult for 10p using contactless.
My 11 yr old child has a zip oyster card that I loaded with £10. The journey cost him 75p. Don't get it?!

Have you made previous journeys today and that 10p takes you to the cap for a daily ticket?

It takes 10p initially and then calculates the full fare later. You will be charged based on where you travelled from/to.

I had one of these last week, but looking now it has gone to £6.60 for the day, which is what I would expect.
Not sure why, but expect the right amount to come through tomorrow

The 10p is sort of an active card check as I understand it, the full cost of your day's travel will likely come through tomorrow.

Will show tomorrow

As above it's like when you pay at the pump for petrol and it's authorises your card with £1 until the next day.

Oh I see! Thank you 🙂