I thought the same thing so I just googled it.
Who can be on List A?
A maximum of 25 players, two of whom must be goalkeepers. There are a minimum of eight places reserved exclusively for 'locally trained players'. If a club have fewer than eight locally trained players in their squad, then the maximum number of players on List A is reduced accordingly.
What's a 'locally trained player'?
There are two categories:
1. Club-trained players – players who were on a club's books for three years between the ages of 15 and 21;
2. Association-trained players – players who were on another club's books in the same association for three years between the ages of 15 and 21. No club can have more than four association-trained players among their eight nominees on List A.