Rule 312.6

Each vanguard card has a hand modifier printed in its lower left corner. This is a number preceded by a plus sign, a number preceded by a minus sign, or a zero. This modifier is applied to the starting hand size and maximum hand size of the vanguard card’s owner (normally seven). The resulting number is both how many cards that player draws at the beginning of the game and their maximum hand size.

Find this number in the current Rules