Everything on your own profile is most likely “Certain,” if you know your names, dates, parents, locations, etc. Certain means it is a provable fact. As you go back into the past you may not have that same level of knowledge and documentation, so some of those items on a profile may be uncertain if different records have conflicting dates, locations, or relationships. In those cases you could make a determination which seems to be correct, but mark it Uncertain and explain why in the text of the biography.