This is the step that decides whether everything else Bloomkeeper writes sounds like your shop or sounds like software. It is worth doing properly.
Bloomkeeper does not ask whether you are "friendly" or "formal". Nobody can describe their own writing voice, and the answers do not help anyway.
Instead it reads what you have already written:
From that it keeps your actual sentences as examples, and works out your habits: how long your sentences run, how you open, how you sign off, whether you use contractions, and the words you never use.
The single best material you can give it is a handful of real replies you have sent customers. A delivery question, an apology, a substitution explanation, a thank you. That is where your voice is most itself.
Personal details are stripped out before anything is stored. Names, addresses, phone numbers and order details are removed. Bloomkeeper keeps the way you write, not who you wrote it to.
Bloomkeeper then shows you two versions of the same message and asks which one sounds like your shop. Both will be plausible. Pick the one you would actually send.
A handful of these teaches it more than any questionnaire could. If neither sounds right, say so, and it will try again.
You can redo the brand voice step at any time from Brand voice in the menu. Worth doing if your shop`s style has moved on, or if you rushed it the first time.