A more prudent assumption would be 10% of that 14% will actually pay for your product when it is launched.
I learned this first hand. Your mileage may vary of course, but it's incredibly easy to drive traffic and stimulate interest, enough that people will give you their email address or whatever other personal information you want. The moment you ask them to pay though, you're in another world in terms of conversions :) This MVP-type google ad testing doesn't really translate that well into real world data like purchase conversions. I don't think that's the point anyway.
It's good for seeing what people might be interested in, which is often something that startups aren't sure of :)