Subtracting a day from reservation

Are FP’s linked to a specific reservation or are they linked to having any onsite reservation for booking 60 days out? Scenario: We have our trip booked and I am going to have to remove a day off the front end due to a work issue that won’t let me leave until a day later. Will I lose the rest of my FP’s when I shorten my reservation? Situation is I am 10 days out from my reservation and I am going to have to cancel day 1. So my trip will now start in 11 days.

You should be fine,