This formula leads to the UI field not populating (remaining blank) if either field value is 0. The referenced fields are Salesforce Formula fields. I have worked around this by adding an artificial 1 to each field to ensure a non zero answer, then subtracting them back out in the UI formula.

VALUE(((VALUE({{SCORE__c}}) + VALUE({{SCORE_2__c}}))/20)*100)

VALUE(((VALUE({{SCORE__c}}) + VALUE({{SCORE_2__c}}))/20)*100)