My time-counter for each mission is another. So each of them shows its own time, until they can be done again. (That's what i was seeing, think so. Correct me, if i'm wrong. Still testing and learning something new every minute.
Edit: And the line i make bold, from Anulmentor. So an own counter for each mission, plus additional 24h waiting time for the other (already completed) missions, if you complete one.