When using 5% acetic acid (aka household vinegar in the USA), you use about 110 ml to reduce the pH to ~5.6. Sorry wasn't clear. 110 ml of 5% vinegar per gallon of milk.
Acidify more isn't about time; I meant about acid. It's like I tried to say, 5.8 for citric and 5.6 for acetic before adding rennet. Meaning 5.6 is more acidity than 5.8. You have to acidify more with acetic because of the pKa differential to have the right texture.
there is no single "ideal" pH for a mozz. Depends on milk... it's a range. If your milk is crap and you direct acidify, typically, you have to do it between 5.6 and 5.8. But say you have sheep or buffalo milk. You can go lower, because the proteins buffer more. For goat milk, it's about the same as cow. Start out with those targets and adjust up or down if you don't like it. Keep in mind, cultured mozz is different.
why do you think goat's milk is not as acidic as cow milk? You mean in terms of pH or TA?