No, Ayemenk, he means in the atmosphere node.
This is an importand aspect to clouds that I picked up from Matt: If you see grain in the dark parts of a cloud then you need extra atmo samples. If your white, lit parts of the cloud are noise-free then you need not apply more cloud samples. The atmosphere is the problem here. I'd think about 80 samples would be fine for this image as it isn't too dark.