Notify Now Element
This element is a simple Go To element with the condition event_seconds < 900. When the condition is met, it goes to the element Text Alert.
Because the Text Alert element hasn't been created yet, you should create this element later.
Wait 15 Element
This is a simple Activity element with a wait action.
Here we are using the timer wait action. This action causes the workflow instance to wait a given amount of time. Once this timer has passed, it will either execute the next action or go to the next element in the workflow. In our example, we set time to be event_seconds - 900
Notice here that the timeout is specified in an expression: event_seconds - 900. The expression event_seconds - 900 can be thought of as the amount of seconds until 15 minutes before the event. So when event_seconds - 900 seconds have passed, there will be 15 minutes left until the start of the webinar. At that time, the element will end its wait action and flow down to its child element.