la_angel is correct. The link is somewhat deceiving, as it's not a calculator at all! It's simply Purlz "tester" implants that you can put in your bra, so you can see what you would look like with a particular implant size.
I like that the last statement to describe them is "Purlz are FUN to wear". I'm sure when you slip these testers in your bra it's like a party.