What is the reasonable person issue in the context of delayed discovery?

Alinsod argues the reasonable person issue is a question of law and based on the evidence in the record only one conclusion can be reached, that plaintiff was on inquiry notice more than a year before she filed the action. But fact finders customarily decide what a reasonable person would know or believe. (See Cotran v. Rollins Hudig Hall Internat., Inc. (1998) 17 Cal.4th 93, 107, fn. 3.) There is both a jury instruction (CACI No. 455) and a verdict form (CACI VF-410) where the jury makes factual findings as to delayed discovery.