This was painful to watch...
But she did say something that is correct, if the tyres on your car are too small or too large, your speedo can be out by 10 kph/mph.
But there are factors such as, how many times did you stop , for how long did you stop, was it at a progressive speed etc.. but generally, if you had the correct tyres on your car, didn't stop within that entire hour...jesus is she dumb.