They've already posted a tweet-rata saying it isn't supposed to work that way.
Unfortunately at this time the PHB disagrees with them.
This is what happens when someone does something stupid, they should have just used a d12 or if some smartass was thinking double dice per level might be something to try, they should have worded it not to be based on per die but per level. IE expand 12 levels of Barbarian for 12d12+ConMod or 12 levels of UA Ranger for 24d6+ConMod.
Sorry if I misunderstood your post and you said exactly the same.
By RAW short rest allow you to regain Hit Dice (capital letters) plus Con mod.
For ranger it's up to (2d6+Con mod) multiplied by amount of levels he have.
So for first level ranger it's 2d6+Con mod, not 2x(d6+Con mod).
BR,
Pelzak