Please do not charge daily to 100% to get the highest range. Batteries like to be in the middle of their charge level. Tesla says there is nothing wrong with 90%. If you have a 310 mile range, that would read 310 * .9 or about 279 miles (what you are seeing). Looks like they may now be upping the range slightly with newer software, so you may eventually get better than 279 at 90%. Not this is an EPA "rated" mileage and is under idea environments, just like the EPA mpg rating is.
BTW, this forum is full of anxiety and worry over mileage range and battery degradation. I wouldn't get stressed over what you read here. The Tesla battery pack has continually shown to be the best in the business. Antidotally, it appears only a small percentage have real issues but it does happen just like with regular cars. The recommendation is to simply drive it and enjoy it. Personally, I like to have the charge in percentage instead of miles as that is what most are used to with a gas gauge.
To better know your expected range, there is an "energy" app in the app drawer located in the bottom of your screen. It will show what your expected rage is based on your driving style and environment. It will take into account over the past 5, 15, or 30 miles how hard you press the accelerator, how many hills you went up (and down), how cold or hot it is, and if you use the AC, heater, etc. That will be a MUCH better predictor how many miles you can expect out of your current "tank".