yup, in simple terms thats all it is.
but you need to know what final vg/pg you want. what nicotine you going to use and what final nic strength you want it to be then let a calculator work it all out for you to tell you exactly how much of each % needs to be added.
a cheap pair of scale will come in handy. bottom post 6 here POTV Vendors & Recommended E Liquid Suppliers