When the instructor assesses you for competence after training, you will be assigned a competence grade. But perhaps you are there but maybe not quite there with unlimited ability.
For example perhaps you are a great skipper in everything except stronger winds. In that case your instructor may sign you off as a skipper but place a provisional restriction on you such as cleared for no more than 12 knots of wind - or perhaps no more than 2 miles offshore.
Provisional restrictions are attached only to Skipper rank.