Lectionary confusion

Yesterday I was greatly confused over the Sunday Gospel reading. According to the OCA web site:

27th SUNDAY AFTER PENTECOST — Tone 2 (10th of Luke). Monk Martyr and Confessor Stephen the New of Mt. St. Auxentius, Martyrs Basil, Stephen, two Gregories, John, Andrew, Peter, Anna, and many others (767). Martyr Irenarchus and Seven Women Martyrs at Sebaste (303). Bl. Theodore, Archbishop of Rostov (1394). Martyrs Timothy and Theodore—Bishops; Peter, John, Sergius, Theodore, and Nicephorus—Presbyters; Basil and Thomas—Deacons; Hierotheus, David, Chariton, Socrates, Comasius, and Eusebius—Monks; and Etymasius, at Tiberiopolis (8th c.).

Luke 13:10-17  (Gospel)

That's the story of the woman who had a spirit of infirmity for 18 years and I was all set to preach on that.

But our diocesan lectionary had

Luke 18:18-27

That's the story of the rich young man who asked Our Lord what he must do to inherit eternal life, and it was in our gospel book under the 13th Sunday of Luke.Except that it should have been the 10th Sunday of Luke, or was it?

Anyway, I had to ad lib the sermon on the Epistle and the many martyrs of the day, most of whom were victims of the iconoclasts.

But can anyone explain the discrepancy in the lectionaries?