Not trying to shut up the conversation, because we all learn from questions and answers, but you can download the User Guide. I keep a PDF version on the computer and it’s helpful when I forget things.
Yikes, doesn’t leave you much leeway. But in your Settings > System Setup > Alerts/reminders (US terminology may differ), you can adjust how low the reservoir goes before you’re alerted, and also how much time before the pod expires you get alerted, both of which are helpful for avoiding situations like having just half a unit left.
Yes, it was 5. The OmniPod's "reserve tank"