Dear @Nunu_12
What is your assignment? I suppose it is obtaining a y+ = 1 or 30 in the first element from the wall, right?
The way you are setting your addLayers control is the following:
If you only set the number of elements, the first layer element will still have the same value, therefore the behaviour will be similar with 20 or 5 elements. So what you need to do is set a thicker first element.
Still, regardless of what Fluid Mechanics 101 said, you will never achieve a specific y+ value with the values mentioned by him, but a rough approximation.
If you need to achieve a specific y+ value you need to calculate the boundary layer size and estimate the y+ 1 and y+30 sizes and set the first element to that size (or calculate it through relative layer size). Here the number of elements may be irrelevant
The calculation of the y+ value is not easy as your case is not a flat plate but a couple of simulations + flat plate calculations should give you a good approximation.
The y+ value will not be uniform through the airfoil as the boundary layer grows in size downstream (and in low-pressure regions downstream the maximum thickness point). Neither will it be the same in the upper and lower faces.
I hope this helps,
Jairo.