The time per lap was calculated by measuring the time for seven laps and dividing the total time by seven.
total time

It is given that the precision is of 0.1 s. it means it is correct upto 1 place beyond decimal.
So, the actual value could vary from 457.800 s to 457.899 s i.e. the time per lap could be 65.400 s to 65.414 s
It means measured time 65.414 s has maximum error of 0.021%. Hence, the measured value is quite precise.