Which version of Cura are you using?
You can increase the "Bottom/Top Thickness" to a multiple of "Layer Height" that works out to more printed layers when closing the top.
For example, to get 6 layers on top with a layer height of 0.2, use bottom/top thickness of 1.2. If your layer height was 0.12 with the same bottom/top thickness of 1.2, you'd get 10 layers closing the top surface.