Making a starter

[Nola_Brew]

I have a vial of WLP515 that I will be making a Belgian PA on Friday. I've made three starters in my young brewing career but never really saw any activity. I do use a drop of fermcap and a little yeast nutrient.
I usually leave the starter on the stir plate for two days, then transfer to mason jars.
My question is how do you determine when the starter is done and ready for use?

 

[Ozarks Mountain Brewery]

usually there will a small amount of foam in the middle of the vortex and the that should go away when done also the color will turn a cream color when done and after cooling undisturbed you should see at least a 3/8 to 1/2" of slurry in the bottom depending on the diameter of your flask, most times its done in 12 hours for me

 

[Nola_Brew]

Thanks. That's what I kind of figured but wasn't sure.

Using Homebrew Dad's calculator, I need to pitch .393L into a 2 gallon batch. The mason jars I have do not have markings on them. Would it be safe to use 1 oz= 30 billion cells? According to Mr Malty, I would need 73 billion cells which would be approx. 2.5 oz.