Hi. I have a 30ml bottle of 8mg nicotine e liquid and I would like to cut the nicotine to 4mg nicotine e liquid. My base is vg so I'd like to stick with that. How do I go about doing that?. Is there a calculator that can do that? I found a calc. on this web site but I can't get it to work. It requires some program not on my computer. Thanks.