How to set world center and scale?

Hi. I'm recently working on adding AR-based camera control feature into my game.

I checked Vuforia Ground Plane sample, and succeed to getting basic AR work.

My game world is located at (0, 0, 0) and camera can move around my game world. The problem is that initial ARCamera is located at (0, 0, 0) and the position of first-anchor is relate to this ARCamera's position.

So first-anchor is located at non-(0,0,0) so ARCamera is moved around first-anchor.

How to sync AR-space center and scale to my game-space center and scale? (without modification of game-side position and scale, it's hard work..)

(especially, I want to set AR-space center to first-anchor and set its position to (0,0,0), and change AR-space scale to see entire game world (about 200x200x10 unity space))