Custom row does not like custom format

Hello,

Trying to format a custom row. I enter 1/20 + 3/10 + 3/10 +3/10 + 1/20

WPBakery doesn’t like this but it does add up to 1. Am I doing something wrong or his custom formatting quite limited?

Is there an add-on that would give me much greater control and precision over custom row formatting?

Thank you for your suggestions.

Best regards

Chris