Importance:
AWA
AWA explains how 'restore full delivery' works.
AdWordsAdvisor Says: [
Link to quote]
After making appropriate changes, if you click the 'Restore Full Delivery' button and the message and asterisks don't go away - trying logging out of your account, then back in.
Also, remember that the Restore Full Delivery button will *not* restore disabled keywords (those with one red asterisk). You'll need to delete all your disabled keywords before Restoring Full Delivery.
IMO, deleting disabled keywords is a good habit to get into. Disabled keywords can work against you: for example they are budgeted for in the calculation of the suggested budget, even though your ad is not showing for them.