No, you didn't understand...
with Denoise set as "Only remove fireflie", you have only one parameter: "Denoise amount"
But, I would like to have a new parameter, like
Denoise threshold.
So, you can tell to Corona, how much bright must be the pixels, to be removed.
For example, I had much better result with Photoshop, than with Corona...
"Full denoising" is another, completely, different story.