How do I create a running total that looks for characters

I have a field that returns multiple values so I could get anything from "1" or "4" or "1&4" or "1&4&6" or "2&5"

Would it be possible to create a running total that would only count the field if it included a certain character like "1"?

I tried this formula but it just returned 0

If '1' in {user_values.markets} then 1

Thanks