Ugly 'steps' in darker zones. How to avoid it?

Hello,
I’m creating a level whit baked lighting. These are my light settings:

The scene is a bit dark (that is my intention) but the darker zones presents an ugly step, they are not smooth shadowed. See image:

In the game the steps are much more clear. More cleary remarked in this image.

How can I smooth the darker areas?
I’ve tryed incresing the Atlas size but this does not work.
Thanks!!

may be try increasing ambient intensity more or indirect intensity

Uncheck “Compressed”. But be ready for your build size to pump up.

Steps01: Edit>Project Settings>Player
2475067--170471--Steps01_PlayerSettings.jpg
Rendering Path : Deferred
Color Space : Linear
2475067--170472--Steps02_CameraSettings.jpg
Steps02: Main Camera Settings : HDR must on.

Use good image effects for exposure like tonemapping.