You have to make a loop. Make a state that creates one object, then loop through that state 10 times.
I've attached a simple example as a screenshot.
There's also a working example in PlayMakerSamples\TestLab\Spawning\SpawnGrid.
There's another example of a loop in PlayMakerSamples\GUI\Countdown.
I would play with a simple loop first just to get the hang of it. Once you get the hang of it you can do more work inside the loop (space the created objects out, pick a random spawn point etc.)