I don't get it. So if you had bitcoins on that particular date you will own clams?
Yes, exactly that. If you used the bitcoin-qt wallet it's quite likely that more than one of your addresses had coins on that date (change addresses, etc.), and so you'll get more than one set of 4.6 CLAMs.
Even if it has nothing currently in there?
So if a address was owned by me at that time but it has nothing in there currently, I will still own CLAMs? Does it have to have some bitcoins in it at that date, or just the ownership of the address?
Sorry for some silly questions.