KVA as already explained is kilovolt-ampere, or the apparent power in wattage the transformer is capable of delivering on a continuos basis. Since your service is rated @ 200-mps, it is theoretically possible you could demand 48KVA from a 15 KVA transformer, which does not appear to make since. It is like writing a $48,000 check with only $15,000 in the account. However a utility company will never size a residential transformer to the size of the service. The transformer does seem undersized, as I would suspect to see at least something along the lines of 20-to-30 KVA for a 200-amp service.

From a safety point of view, you are not in any danger. If you overload the transformer, the transformer fuse will operate and put you in the dark. Your 200-amp service (common size for medium sized homes) was selected based on the size of your house and the computed load that is possible. If during the summer months you notice your light staying dim while both AC units and electric stove are on, report it to the utility and they will investigate and determine if they need to upsize your transformer.