mark (something) as
To place a mark on something, or next to something's name on a list, to signify its state or condition. It's a tedious task, but you'll have to manually mark each item as new, used, or unknown. Go through the list of names of guests and mark each one as either absent or present.
mark something as something
to make a mark next to the name of something on a list indicating what the thing is. I will mark this one as expired. This one is marked as needing repair work.