In some cases users may see that entering decimal values (for example .5 or 0.5 or 1.5) in Tone Mapping parameters inside VFB doesn't work. No values will be registered when entering them in "dot-number" fashion.
This may be caused by having the Grouping Symbol in Windows Settings > Region > Additional Settings set to "dot" instead of "comma":
Solution:
Changing the grouping symbol to "comma" ( , ) instead of "dot" ( . ) should resolve the issue.