Check first that the HRM is in good working order then if it is think about this
RHR is taken at night when you are alsleep so if this is the case that doesn't sound all that weird to me. As we become more fit the stroke volume will increase thus decreasing the amount times the heart needs to beat to get the oxygen to the body. But if this is something that is taken while wide awake and just sitting there you need to do like the above have said. Get it looked at.
Velocity