Blood Donation Time = More Worries

The craniofacial surgeon sent the paperwork for the blood donations today.  I may have a Master's degree, but this stuff is confusing me.  Can I chalk it up to being tired right now?  One thing that leapt out at me, though, is that they do not advise using the same donor twice.  What do we do, then?  We have had 3 people do directed donations for both surgeries.  On the second surgery, two of them donated, and both units got used.  On the first surgery, three of them donated, and two units got used.  We know whose one of them was, and we are not sure about the other.  Who do we call?  What exactly is the risk of using, possibly, the same donor three times?  How am I supposed to sleep at night with these sorts of questions bouncing around in my head!?