ISB ~ Revelation 6 v6

denarius:A full day’s wage (Mt 20:2) buys only a day’s ration of wheat for one person and a ration of barley for a small family. Limited food supplies and inflated prices are sure signs of famine.

oil and wine:Crops harvested in late summer (olives and grapes) are not to be devastated like the crops harvested in late spring (wheat and barley). A limit is set, lest the famine overrun the entire harvest season.