The conditions are not at all the same.
Condition #1
The scheduler checks the current idle state. Has the computer been idle for at least 15 minutes? In this context idle means there has been no user input and the CPU usage has been below some low level. If this condition is true start the task. Otherwise continue with condition #2. This condition is to prevent a CPU intensive task from running while you are buy with for example a demanding game.
Condition #2
This occurs only if condition #1 fails, the computer is not idle. The second value of 1 hour is how long to wait until the computer is idle. The scheduler now waits for condition #1. If that occurs within the specified time limit of 1 hour start the task. If that does not occur it is time to give up and wait until the next scheduled time if such is configured. This condition exists so that an important task is not skipped if the computer happens to be busy when it is scheduled to run.