In message , at 15:09:58 on Thu, 2 Mar 2017,
tim... remarked:

When you use a brand new card a 10p authorisation, but not charge, is
made against the account when you first touch in. Nothing else reaches
your account until the end of the day when a single charge for the sum
of all the journeys made is collected and the 10p authorisation cancelled.

so what happens in the back office if the charge for 28.60 (the cap for
Shenfield to Zone 1) is rejected?

do I get free travel for the day

No, you might get an unauthorised overdraft on your credit card, and
quite likely a penalty charge from the card company.

And TfL will probably blacklist the card, so it won't work "tomorrow".
--
Roland Perry