Used the GNE M-ticket app again today. Have to say it's faultless. It does leave me with a question though!

I notice GNE drivers press something on the ticket machine when you board with an M-ticket. Journey recording I'd assume? I also have a monthly m-ticket with Arriva, and notice they don't seem to record the journey all? I often just stand at the front of the bus and never see anything pressed on the machine.

Does anyone (perhaps drivers) have any light to shed on how these journeys are recorded across all companies that accept mobile tickets?