When I did my A&B in 1959, the 18 pre-solo launches included 3 simulated cable breaks at various heights, logged at 1 minute each. That tends to push the average down.
The 3 solos added up to 14 minutes, a solo launch gets rather more launch height.
(Average solo flight time in 2017 was 4 hrs 15 or thereabouts, but all in somewhat better performance machines).