Apologies for missing this question until now.

When you zoom in/out, the target size changes, as well as the tombstone at the bottom right.

Here's a shot of it zoomed in a bit while looking out the same office window as above.



You come across an elk, you line up the two two horizontal lines and work the zoom until the elk fits between them (shoulder touching the top line, breastbone touching the bottom line). When you're done working the zoom for fit, read the bottom of the tombstone.

In the above pic (assuming I fit an elk in the lines), that would be 350.

Here's a screenshot of the first two pages of the fold-out flyer. Note the location of Mr. Critter between the first two lines.



After that, turn the top turret, elevation, to the tick mark between "3" and "4" and we're on-target for that distance.

In theory.