It doesn't really mean anything. Providing your heart rate
is regular its unlikely to be anything to worry about. Too much empathises is given on heart rates having to be within a certain range. Are you taking any medication at present? If you are very fit and athletic, your heart rate will be lower than average. Mine is about 46.
I've actually seen some cardiologists giving drugs to people just because their heart rate is slightly outside what is considered 'normal' range. It's only as I study more I have come to realise just how unnecessary it is.
Unless you are experiencing any other symptoms, there is nothing to worry about.