So, if you mean accurate in predicting range it all depends on how you drive and what you use that drians the battery - e.g. heater, aircon etc. Under eco the hvac is reduced for example. It’s just a prediction based on historic mpk data - nothing more.
Depending on how you drive and what you have switched on you’ll achieve a certain range. Look at what mpk you typically achieve. Say you average 3mpk then you should have a useable range of about 120miles as long as you use the car in the same way. Warmer weather will increase the useable range too. As in all cars if, for example, someone else drives your car in a completely different way then the range will obviously change accordingly.
As far as charging using the granny - you get about 3.5kw/h. So 14 hours should normally fully charge your car. Check your HV pack voltage after a full charge - depending on what BMS software you have it should be c449v or c454v. Your predicted range looks ok but as prevoius;y mentioned it’s based on historic data. There’s lots on the forum about BMS and charging/equalisation and I’ve only scratched the surface. There have been cars with faulty BMS. If you have any concerns get your dealer to check it out
