I'd give a flock that size 1/2 of the scrap at once if you haven't simmered it off and picked it as clean as you can or all of it if you have salvaged everything you can.
I always keep my feeders full of their normal all-flock 24/7/365.
Since meat scraps are primarily protein I balance that with the carbs of the scratch. It's not necessary, but I consider it a well-rounded treat that way. :D
How many chickens do you have?
I have a large flock so I just put the picked over carcass and scraps into a dish, set it in the run, and let them do what they want.
I often mix large volumes of meat scraps with scratch to balance out the day.
They will pick the bones clean but don't eat them...