Optimisation score is an estimate of how well your Google Ads account is set to perform. Optimisation score runs from 0% to 100%, with 100% meaning that your account can perform at its full potential.
Along with the score, you’ll see a list of recommendations that can help you optimise each campaign. Each recommendation shows how much your optimisation score will be impacted (in percentages) when you apply that recommendation. Applying or dismissing these recommendations changes the overall optimisation score of your account. Optimisation score is available at the Campaign, Account and Manager Account levels.