First of all, if all the rule is doing is translating from 33 to 1 and so on, why not use a Transform? I don’t know if the KNX binding supports transforms but there is a transform Profile and this looks like it can be a simple map. But if not maybe a JavaScript transform is needed (I don’t understand the switch statement).
I do note that this rule will run twice for every change. First when the Item changes to 0 (for example) and again when this rule updates the Item to 33. For this reason this is often why a Design Pattern: Proxy Item is usually used for cases like this.
If for some reason you cannot use a transformation, see Design Pattern: Associated Items for approaches to handle all the Items in the same rule.