There are 15 points of Neutral Agenda, and with a deck size minimum of 45, at least 20 Agenda points are required to be present (allowing deck sizes from 45-49).
Jinteki and Haas-Bioroid have no leeway in their Agenda choices. Both of their single in-faction Agenda are worth 2 points, so they must include all three faction Agenda and the six Neutral Agenda.
Weyland only needs 5 points in faction Agenda and can do that with two in-faction Agenda of 1 point each. With two CORE sets, Weyland can choose which of Corporate Takeover and Posted Bounty is represented only two times, or may choose to include 3 of each with no change in maximum deck size.
NBN has the most leeway, and can choose to include from 5 to 9 'in faction' Agenda Points across their two Agenda (worth 1 and 2 points respectively), giving them 20-25 Agenda points. If NBN were to include all of its in-faction Agenda at x3, they could get up to a 55-59 card deck if they so chose.
Agenda : Deck Sizes