Today I had a message saying I had around 390 miles of Adblue but I had a long trip today and ended up playing "Adblue chicken". When I got back home the message was stating emergency operation in 4 miles. So I'd expect the Adblue graphic to be showing hardly any when it actually shows that the Adblue level is just under half full. This seems a little on the over-cautious side to me but I'm not sure what would happen if the message goes to / past zero even though there appears to be plenty of Adblue left.