Goals over 18 add 1 success per point about 18. Thus a person with a goal of 20 gets +2 successes to their roll. This is for parity purposes - in all other parts of the rules, successes are calculated first, then VPs determined. For goals above 20, however, VPs are added on -after- calculation, and that can be solved by making the above clarification. It changes no rules with regards to VPs, only with regards to contested rolls.