APY = annual percent yield
That is, the yearly return on the investment.
I believe it is referring to a
monthly interest amount, but that is a bit ambiguous.
If interest rates are being forecast, they must be based on something. Let's assume it's the
prime rate, as that is what is most commonly used. (Unless they don't actually
mean forecast, but that's a separate problem.)
I would add a "the" before "interest" in the second sentence. Assuming I am reading it correctly, it is saying that if you give it a required APY, it will tell you what the monthly interest is (I don't believe there IS any difference between "interest" and "interest amount" in the way they're using it) and what rate of interest would give you that return.
But Glynn is the person to ask this kind of stuff. I'm just making a (somewhat) educated guess.