the oscillator is bound between 0 and 100, overbought is considered above the 80 level. On the other hand, oversold is considered below the 20 level. Therefore, cross downs that occur above 80 would indicate a potential shifting trend lower from overbought levels.
Likewise, a cross up that occurs below 20 would indicate a potential shifting trend higher from oversold levels.
Likewise, a cross up that occurs below 20 would indicate a potential shifting trend higher from oversold levels.