Hi Laura and welcome to RootsChat
I'm no expert on Scotland records, but many chatters are. But someone is sure to ask
How are you sure the two entries are for the one person?
Are the dates identical?
Are the parents identical?
If an address is part of the certificate, are they identical?
If the answers to the above are all yes, I'd hazard a guess that mum and dad both registered the birth but at different offices, and nobody picked up the duplication. Then again, I may be quite wrong!

Dawn M