Hello and hope you are doing well.
The normal sleep requirement varies with individuals and if you feel fresh and well rested after 6 hrs, then that should be your requirement. You could be having an entity called delayed phase syndrome, where in the biological clock is reset and occurs late. It is a circadian rhythm disorder. There is a circadian rhythm for all living organisms. It is a 24 hour cycle rhythm and the biological clock within that individual adapts to this rhythm. This can be reset by bright light therapy, sleeping pills and sometimes by sleep debt. In sleep debt, though you happen to sleep late, you condition yourself to get up early; this in turn will help you to sleep early. So, try this, but if your symptoms still persist, I would advise you to discuss your symptoms with your primary care physician who may then refer you to a sleep specialist for further evaluation.
Hope this helped and do keep us posted.
btw.
Male : 25 just in case