ADE7751 gives a output pulse for each unit of energy measured. This pulse can either be used to drive a stepper motor type mechanical counter. Alternatively this counter can be fed to your microcontroller, micro can then keep on counting the number of pulses received from ADE7751 and display the energy consumed on say LCD or in your case of prepaid meter you can go on duucting debit amount per pulse you receive.

Regards,
Prahlad Purohit