Look normal RBC count is 4.7-6.1 millions per microlitre of blood. Yours is not significantly high actually. The causes of increased are varied ranging from smoking to congenital heart anomaly and it can happen without any actual cause also. From the data you provided, I can not say confirm that there is no abnormality, but most probably there's no such serious issue, still you can confirm it by doing proper investigations. And regarding blood donation, it's fine to do it and it will prevent the hazards associated with high RBC count like increased viscosity of blood.