Best answer by woz
The numbers don't carry on from the previous meter; when the smart meter was fitted it will have started from zero, and your old readings will have been given to Shell for billing.
The numbers shown on the new meter assuming you've read the right numbers are the ones you should submit to PP.
Where you may find a problem is if the SM was fitted in the near past the meter database may not have been updated yet. It can take quite a while so when PP switch you over they may have the wrong meter info, and you'll need to send them photos of the new meters.
Thanks for this, managed to get a display up but seems very low numbers, was expecting them to carry on pre smart meter. Will contact Shell and see if they can help.