Your device has received its last automatic update. (ie.- Your computer is going to die slowly and excruciatingly both for you and the machine.)
Over the years, Chromebooks update automatically to keep the software secure and speedy, and provide you with the latest features. Your Chromebook has now received its last automatic update. (because we want to be richer and have you go out immediately and buy a new computer although this one will probably last a couple more years but with weakening security every scammer in your neighborhood will try to scam into it.)
What it means (you are a sap and will go out and buy another computer. Do you give money to Trump too?)
When your Chromebook receives its last update, you’ll receive a “Final Software Update” notification. You can also find this date in your Settings menu under Settings > About ChromeOS > Additional Details. From this date, you can continue to use your Chromebook but it will no longer receive security and feature updates. (And someone from North Korea will break into your bank account and drain it.)