Chronic osteomylitis, bone marrow biopsy normal, jak-2 mutation negative, erythropoitin level normal, s.Ferritin level 5 but hb.17.8.What is its reason?

Many possibilities. Your question is why your hemoglobin is at the top-of-normal (or maybe a tiny bit above) for a person of your age and gender. I'm much, much more concerned about your chronic osteomyelitis. I'd consider a right-to-left cardiac shunt, osler-weber-rendu lung shunt, sleep apnea, high-affinity hemoglobin, an obscure mutation. It's not dangerous in itself & could "just be you.".