This oscillator value (OSC) is simply interpreted as a rate of change against the exponential moving average. The interpretation of OSC is similar to another technical indicator, Momentum, which also measures the rate of change of the security price in a given period of time. The relevant formula is:

Generally speaking, when the OSC is falling, it implies that the security is suffering from a weakening trend. When the OSC is increasing, it may imply the security price is becoming stronger. It will be more accurate to observe the reverse of trend when there appears a divergence between the trend of the price and the OSC value. In other words, when the price is falling but the OSC value is rising at the same time, it indicates that the trend may reversed in the near future, and vice versa. The Chart shown as below is a good example (i.e. "Cathay Pacific") to explain this phenomenon.

We have defaulted 10 days for the calculation of the Exponential Moving Average. You can also set your own defaults in the appropriate box as indicated by the cursor as shown below.