One round from every match, chosen by a pure function of the replay bundle — not by whoever was watching. Two people cutting the same match get the same clip, and the choice can be argued with rather than being a matter of taste. The reasons are printed on each card.
Clips are cut by a separate worker reading the bundle directory, so a wedged video encoder can never stop the league taking bets. Every clip here has a bundle behind it that you can re-run yourself.