Amish friendship bread

A friend of mine gave me an amish friendship bread starter. I was really excited! I had some for the first time last year, and it was delicious!!!!

So anyways, i'm just confused as to how we can eat it, and not end up puking our brains out. Basically, you are given a starter. It has a cup of the mixture in it from your friends starter. It's kinda confusing! Anyways, it has instructions, but you let it sit out for 9 days. On day 5 or 6, you add a cup of milk, sugar, and flour. To make a long, rambling, confusing story short....basically you could be eating a loaf of bread that has milk it, which could possibly have been sitting out on the counter for months!!!! Make sense? So say I got a starter from a friend, and she got hers from a friend. On day 9, when their starter is done, you add more milk, sugar, and flour. Then you take out a cup of mixture, and put it in 4 seperate bags. Voila! 4 new starters! Then I give a couple of my starters to a friend. Although the amount gets smaller, and smaller...their still is a trace amount of milk/mixture leftover from my friends starter, and her friends! Are you totally confused yet??? :) Google it if i'm making no sense. But seriously, my question is, how can you eat something with milk in it, thats been sitting out for maybe only 10 days??? When it ferments (whatever that means) does that make it somehow more safe?

All I can picture is a sippy cup of milk thats been sitting in my car for a week. There is NOOOO way I would want to drink that nasty stuff!!!!!! Why is it different with the bread mixture? Someone enlighten me!!!!

My 2 loaves are now cooking in the oven. Regardless of how the heck it works, i'm still excited to eat some! :)