I'll take a stab at it and guess that the 344 miles is based on the EPA range which is usually somewhat smaller than the WLTP range.
There's tons of discussion about this subject here. Once people learn enough about the car to realize that they aren't going to get stranded by the roadside with an empty battery they start worrying that their batteries are degrading faster than normal.
Don't charge the battery to 100%. That will shorten its life (doing it occasionally won't hurt but don't do it very often). 80% of 344 is 275 miles. That's more than enough for 99.9% of drives.