Well this sentence in the announcement says it:
"Confirmation that the majority of the additional General Admission seat capacity, resulting from the expansion of the North Stand for the 2026/27 season, will be dedicated to Season Ticket Members..... and that the majority of the additional GA seating capacity will be held by Season Ticket Members, through the release of new Season Tickets. "
I would take it to mean that at least 4,000 will be new season ticket holders, and:
"As part of our commitment to making sure the next generation of fans can regularly attend home matches at the Etihad Stadium, of the new Season Tickets to be released for the 2026/27 season, we will ringfence a minimum of 50% for Junior Cityzens. "
So at least 2,000 will go to young fans