While we want to be very very fair here, we are also not looking to help anyone find loopholes to this. The simple way to look at this is:
Did I get my 5/5 clear this week in a given raid size (10 or 25)?
If yes → You are done for the week and please don’t try to get more clears/kills in that raid size.
If no → finish your current existing instance and then be done for the week.
So if you full cleared this week, you are done in that raid size for the week. Going back in and trying to find a way to get extra kills is where you might find yourself in trouble, so please just don’t do it. Like I said, we don’t want to overly punish guilds that stumbled into this while progging across multiple raid nights and sessions, but deliberate and willful exploitation is not cool, and you will know if you are doing it.
I mentioned “killing Anub’arak more than once” for simplicity, but we’ll also be able to tell if, for example, someone was able to get 3+ Twin Valkyr kills as well this week within the the same raid size, and can very safely assume they were aware that what they were doing was not correct.
Hope this helps clarify things.