ASM ready to be enforced

They mean that that staging period ends (meaning that that the entity will be shown with a suggestion to be enforced) after the specified time has expired and during that time no learning suggestions have been accepted. So for example: if you have a staging period of 7 days, and 7 days have passed since you last accepted a learning suggestion on that entity, the entity will be "ready to be enforced". Reading your quote from the manual, I think that manual perhaps is miss-leading because it doesn't mention that the staging period is reset to count down again only after a learning suggestion has been accepted. You can have many learning suggestions on a staged entity but unless you accept one of them (and then reset the timer of the staging period to its original time) , the staging period will end after 7 days since it started.