I understand your frustration, and disagree with several of the posts that replied to you - as a one week new car, it doesn't know how you drive so your driving habits couldn't be the reason the gauge is showing 260. Temps could be the culprit, but I live in San Diego, where temperature is rarely an issue and I have the same issue with the gauge never having shown my max/true range.
I picked my car up in October, and now have 3500 miles on it. The range gauge as never shown "247" at 100% charge (I have standard range battery). Most it's ever shown is 230. But I largely ignore it because I know that my car is delivering 3.7 miles/kWhr over those 3500 miles...which translates to around 260 miles range (3.7 x 70), which is actually better than stated max. range for the car. And I have confirmed this number (as shown in my "Trip 2" which I set to zero when I got the car and have not reset it), through the app as well as through the miles driven and kwhrs input through charging on many individual road trips. Bottom line, look at your percent battery gauge and use that in combination with your current condition miles/kwhr data (can use Current Trip and/or Trip 1 as an easy monitor) to accurately calculate your range. For some reason the miles range gauge "guess o meter" others refer to is drastically conservative....in my case its nearly 20% off on the low side. For some reason Ford engineered it that way intentionally.