Item Weight/Unit Count

I have a listing which contains 12 bags of Pork Crunch each at 30g, the total weight of the item is 360g. It is priced at £12.95 (£11.65 with subscribe and save) and the listing states that it costs £388.33 per KG! Where am I going wrong and can I change it so that it states price per 100g as it isn't the best measure at all. Any help appreciated.