Carl,

It depends on the ballistics for the load your shooting actually. 1.8 to 2 inches is a ballpark figure for a 200 yard zero using a 100 yard range. Look at the ballistics for your load and determine what you want your zero to be. Also, depends on your shooting situation. Do you normally get a shot to 200 yards? or 300? or 100? That would be where you zero your rifle for, wherever distance you normally get to shoot.

Cheers
Alex