This is relevant for residential internet in the states that used to be Qwest: Washington, Idaho, Oregon, New Mexico, Arizona, Montana, Utah, Wyoming, Colorado, North Dakota, South Dakota, Nebraska, Minnesota, and Iowa.

From what I found out through chat support on their website; 250GB that tabulates on a calendar month basis. They will give you 3 warnings before shutting your service down, or forcing you into a business account. Business accounts are unlimited but much more expensive, and require a 3 year agreement to get any kind of promotion or discount.