Need help mixing color

I am a student and not sure how to mix this Goldwell color

I am using Goldwell Topchick tube and Goldwell developer,
where I am stuck is, I am using 2/3 B & 1/3 G.
Since the color is in a tube, how do I measure the developer and how much do I use?

honestly i would just eyeball it equal parts developer to equal parts color. if you really wanna measure then go buy a bottle at a beauty supply store. If you're doing this at home you can use a shot glass which is normally one ounce & you'd probably want 2 ounces dye 2 ounces developer depending on the thickness & length of hair.