There are several different ways to rate a pump, up rated HP, max rated HP, full rated HP, brake HP, and so on. The exact same pump can be listed with three or four different HP ratings by using the different systems. The only numbers you can really compare are the brake HP. You get brake HP by multiplying the listed HP times the service factor (often called SF).
It is a 1 hp pump. The rating is really a sales trick. Most motors will put out about 50% more than there
standard rating. The standard ratings area for continuous duty(24/7) and the uprated is for intermittent
duty. It sounds like your a getting a deal but you are not.
Sometimes you can get a deal if you know what you are doing. Often the uprated model of a pump is less expensive than the fullratred model with the same brake HP (i.e. the uprated 1.5 hp could cost less than the 1 hp full rated model even though they are exactly the same pump!)