Sounds like the vendor you purchased from recommends steeping which can help many mixes. You can open the bottle as they have recommended and it will speed the process up but I've never done that nor would.
There are many ways of letting it steep, you can just set it aside for a week or two and it will steep, others put the bottle in a warm water bath to speed up the process. There's many ways people have of doing it, I just set it aside for a few weeks.
That being said steeping may not be needed on all mixes and even if it does help it get better with time doesn't mean it'll be bad when you get it. I'd recommend trying it, if you like it just
vape it, then you can note the change over the time span if there are any. If it does taste off to you then let it steep for a while and try it later.