how we choose the number of direction in each level for contourlet

I want to ask about the way we choose the direction in contourlet for example

levels = [0,2,3,4,5] ;

here they have divided the image to five levels for level one no direction division for level two 2 directions then for level 3 the number of directions is 3 and so one, am I right? because I'm a beginner in contourlet I want to apply the it to denoise my image and I don't know how the number of directions in each level is chosen, if for example I choose

levels = [0,4,8,9,10] ;

in order to have more details is it correct or there is some theory for choosing the number of directions?