At How to set limit for rendering? - 3ds Max in the Corona Render FreshDesk, there are instructions on when a render should end. The third item states:
- Enable Noise level limit for rendering:
go to Render Setup > Scene > General Settings > Progressive rendering limits, set Noise level limit other than 0
However, the instructional image and red outline box below the text does not show a Noise Level Limit setting, because (I think) this is an old image of this dialog box before the setting in question was added. The image should be updated to show the current state of the dialog box with the Noise Level Limit setting included and the red highlight rectangle extended accordingly.