I really don't recognize the jargon they've given you, but it seems to me that your instincts are probably correct. The question is, can you do it both ways, and see if you get a difference? It's important to realize that you might get slightly (or maybe very,) different values. That's why they've asked you to do it both ways, and have to give each way a term. The "dilution method" doesn't seem to be one that I'd heard of.