At the bottom of the popup for every action is a section called Choose timing options:
Timing options allow you to delay execution of an action after it has been triggered. The 4 options are described below.
No delay will be applied.
Allows you to delay the action by a number of days, hours or minutes.
Allows you to schedule the action for a specific date and time. If a contact triggers the action after this date, it will not run.
Day of week
Allows you to postpone an action until a certain day of the week at a specific time. This is similar to Schedule but can work regularly on the same day of the week. Example: You may send a relevant email to campaign contacts advising about Friday offers.
Note: If you change the delay of an action while a contact is in the campaign it will update to the most recent timing option, providing the contact has not already triggered the action, and providing the action is not scheduled to run in the past.