Measure the duration of any persistent trains. Each pair of stars should straddle closely to the meteor's path. Repeat for the other pair. After some practice, you will find that this comes naturally, and it gives accurate results. A being the slowest equivalent to about 2 degrees per second, and F is the fastest corresponding to 25 or more degrees per second.
Numerical estimates are too difficult given the magnification.
The velocities are needed in the radiant analysis. OO means it traversed the whole field. 10 means that the meteor started within the field, but moved outside. Depending on the weather conditions and alertness of the observer, it is best to take longer and more-frequent breaks than visual observers, as telescopic observing does require more concentration, especially when the rates are low. Many new observers don't overcome this initial hurdle and give up.