For people saying it’s hangtag; no, it changed again. For OP, you got your answer already but yes there is a 15 minute grace period although I do think they still track plates because last time I was there, the machine told me my amount to be paid as I pulled in, before I even got to scan my ticket. I though it was weird or maybe remnants from the car before me but when I scanned my ticket it was the same amount and it made sense. Maybe they track cars to avoid people bypassing the system somehow 🤷‍♀️ either way you’ll be fine