local area network traffic was sent out and received by the device to the tune of 1TB of traffic. not internet data but local area network data which is not ideal for a coffee machine either way you slice it. if it were some kind of local bonjour or whatever the open standard is called service that was just alerting the network of their name it would be understandable but the coffee maker is streaming the equivalent of about 17 high def movies every day to the local network.

I mean, it wasn't clear to me without the explanation (I too thought it used 1TB of public internet data), but it's clear now that it is accurate (it literally used 1 TB of private network data)

It might not seem to be anything (people will assume private network traffic is free) but there is a cost - it's capacity that could be used for other purposes, eg. home alarms.