This property tells you how many settings there are for the effect. You can use the count instead of the default enumerator. For example the following code:

Set theFX = Server.CreateObject("ImageEffects.FX")
Set theEffect = theFX("Levels")
For Each theSetting In theEffect
  Response.Write "<br>" & theSetting.Name & "<br>"
Next

Is functionally equivalent to:

Set theFX = Server.CreateObject("ImageEffects.FX")
Set theEffect = theFX("Levels")
For i = 1 To theEffect.Count
  Response.Write "<br>" & theEffect(i).Name & "<br>"
Next

Item property.