I'm too honest

Whilst away in Cornwall, Fowey to be more specific, I paid for lunch for Steve, Jenny and April.  It was pretty decent food and with starters wasn't cheap.  When asked for the bill the waitress entered in the amount then handed the machine to me to enter a tip and then my pin.  I typed in a reasonable tip and it warned me that my tip was over 25% and then asked me if I was sure and wanted to continue.  Despite my mental arithmetic being appalling these days I was pretty sure i'd only added around 10%.  To make sure I pressed the back button then tried again.  The same warning message popped up so I decided just to go ahead with it.  A summary screen had popped up with the cost of the meal and the tip.  The waitress had only entered £0.86, instead of the full £86.  Idiot.  She was lucky i'm far too honest.