Markings around the dial?!
Really?
Believe me, it HAS been discussed extensively.
But providing that the Zion is functioning as it should, you can turn the dial in one direction until it stops, & then turn it the other way, until it stops. Min & max. Simples.
And as long as you know that it does not spin a full 360°, you should be not be tempted to force it further.
So, if you feel no heat, you are at the lowest end - but if you feel heat & get vapor - you at the opposite end.
Once you know where the beginning & end is, it really is not difficult to get used to, imo.
Personally, I like the bare innocence that my Zion exudes when sitting around, cap on. Markings around the dial would detract from this and imo, only really be useful in the first instance.
I believe these current Zions have gone out without any guide or manual in the box - future production will include a quick-start guide which will contain information for reference such as the power dial positioning.
Anyway, Vyvyan is perfectly happy as nature intended.