I had a question on the lottery process, hopefully someone here might have some insight. How does requesting alternate dates work?

I chose Sept 14 as my primary date so I feel pretty confident I'll get my permits. But am I only competing against all others that chose Sept 14 as their primary or does that include those that chose that date as an alternative as well? I probably shouldn't be too worried, but I'm just anxious to get back to the top for the first time since 2012.