Sounds right. Your math and science are not as bad as you think. 20 mls will be fine if you use yeast in the state you suggest and grow a couple liter starter for a day. Have fun!
Thanks! This thread and brewing in general have really allowed me to improve in the areas of math and science, but it's still a struggle for me. I'd been out of school for a lot of years before I started brewing and it's been a great way to get my brain working again.
I can't wait to get my first batch of yeast in the freezer. I'm pretty excited about the whole venture.
And, yes, I plan on making starters each time I brew. I only brew 3.5 gallon batches, so I usually don't have to make quite as large a starter as many folks.
Thanks for the assistance.