How do Calvinists interpret 1 John 2:2 in light of Limited Atonement?

1 John 2:2 (ESV) > He is the propitiation for our sins, and not for ours only but also for the sins of the whole world. Understanding the "ours" as referring to the universal church of believers, it would seem that John is saying that Christ "propitiated" for everyone's sins. Calvinism, through the doctrine of limited, or definite, or particular, atonement, says that Christ died only for the elect. How would a five-point Calvinist understand this passage?