Leaven amounts can alter the level of SOURNESS in your dough!
The amount of LEAVEN in a formula will also determine the flavour profile & speed of fermentation of your dough! So knowing this, with a little practice, you can start figuring out the perfect amount of starter within your leaven & the perfect amount of leaven in your dough to meet your tastes & desired schedule! Don't worry about this now...this is for later!
MORE LEAVEN = more sour dough & faster bulk fermentation
LESS LEAVEN = more mild sour flavour to dough & slower fermentation