This problem was only present in older versions of Corona!
If you are experiencing strange behaviour of built-in VFB exposure controls (ColorMap tab) - for example some parameters change to extreme values like 999:
1. Close 3ds Max
2. In Windows go to Control Panel > Region and Language > Additional settings...
3. Change "Digit grouping symbol" from any symbol that is currently used to " " (SPACE)
4. Apply changes
5. Restart 3ds Max
From now on, the settings should work as expected. If you are still experiencing similar problems, please contact us by submitting a support ticket.