Got 11 out of 11. I'm not sure what that means though.
Didn't miss the pill one Bas -- it doesn't matter whether you take the pill as soon as you get it, or take it later. If you start a stop-watch when you take the first pill you'll see that the last one will be gone 60 minutes later if you take them every half hour.
For example, you decide to start taking them at 3pm tomorrow - one pill gone at 3pm, one gone at 3:30pm, the last is gone at 4pm. Of course you can argue that if you don't start taking the pills for a week they're "lasting" a week, but I looked at it as though they're asking how long the dosages would last while you were taking them.
Ok... I have a headache now, thanks Nial