It looks like the trigger process files in batches, which means that each of the files uploaded doesn't create a new instance of a job. 

• Wait after last change in seconds: The time to wait to trigger a run after file arrival. Another file arrival in this period resets the timer. This setting can be used when files arrive in batches, and the whole batch needs to be processed after all files have arrived.

If you need to process files immediately or separately, you can play with Auto Loader configuration.