Bug?: Format Rules are not applied as intended

[kosuke]

I have created a Format Rules that changes the color when the value in the column [Total Approved budget 1] is 0.
However, even when the value displayed is not zero, the Format Rules are applied and the color changes. This is not the intended behavior.
When I checked the Expression Result in the Test screen of Format Rules, I found that Y/N was properly calculated according to the column values.
When I delete this Format Rules, the color goes to the default state, so there is no other Format Rules changing the color.
Why does it behave this way?
Is there a workaround?

Tip: [Total Approved budget 1] is a Virtual Column that sums the values of other tables.