Why the target offset on the Futures fins install kit?

Hi all. The instructions on the Futures install video says to use the “right” crosshair on the left fin and the “left” crosshair on the right fin, effectively pushing the fin out closer to the rail. I’ve followed these instructions, but I’ve never actually understood why. This question came up for me today while installing fins for which the “fin placement” is based on a board that I previously made. It seems that, if I use the offset, the fins placement will be off. Can anybody chime in on why the offset is recommended in the first place? Thanks in advance.

When you look at your set of futures ‘side’ fins you’ll notice the flat side of the fin (which is closest to the stringer) is over to one side of fin tab.
The tab is the part of the removable fin that holds the angle for the fin and also attaches the fin to the fin box.
When the fin is in the box this flat side of the fin is not in the middle of the box.
Since the flat side of the fin is the part of the fin that is always lined up with the shapers marks, then, the box must be moved over (closer to the rail) to achieve this.

Mr yorky, you’re awesome! That’s exactly what I was looking for. Thank you.

Another realization I thought of, based on this conversation is; if you’re making a template out of an existing surfboard, with future fin boxes, then don’t use the offset. Just put the fin boxes in the same place. If the existing surfboard has fcs boxes then…??? Not sure.