Our ClusterPointStyle is based on the distance, but don't related with the cluster number.
That means, if you assign the style to map, it always cluster the features which met the condition. So you cannot make it only cluster the features more than 5.
Here is the sample I modified, which can shows image for different number, you can modify the value to get different result.
ClusterPoint.zip (223.7 KB)
And if you want to make the style work follow your description, you should want to write a custom style, or you can inherit our style class to implement that.