How does Miami Metro monthly pass billing work?

Hey guys, want to buy a monthly pass on the metro since I have to use it essentially every day - but I'm a bit confused about the billing. It says something about the 20th of the preceding month to the 10th of the following - I'm not sure how to navigate it because today is the 7th of May. Does that mean if I buy a monthly pass today, it will have counted from April 20th to May 10th for the same price? That can't be right. A bit confused as you can see lol.

I asked the employee at the station too but he was new, young and couldn't really explain it to me.

Also when you buy the day/week/month passes, I understand these are unlimited rides on the Metro and bus. What about the trolleys?

Thank you!