UK provisional driving licence

I'm currently filling out my provisional driving licence and need to write in my birth certificate serial number. I have two birth certificates, one has just my birth details and the other has my mum and dads signatures and stuff. Both have different numbers on the top right corner. The one with just my birth details has AC writen under 7 numbers and the other has 7 numbers and then the letters CE in a smaller font size. Can anyone tell me which one to write down? Thank you.