This stuff comes down to personal preference. If unsure what you prefer, you can take off a nug now, label it, let it dry. Repeat that process at different stages. Take the bulk at a particular time if you want, but can take a nug or two before/after, too.
Some plants won't amber up. so if the calyxes have been fully plump for 7-10+ days, that's when i start to consider the plant won't amber up -- it's not common.
Use other observations - pistils and density of buds.
also, remember to only look at trichomes on the calyxes. You want someone to say if a then b, but it's a range of possibilities and your own personal preference that selects when to harvest. Get on that bike and learn to ride.