Best practice is to approach the line on close hauled, with bow calling the cross.
So, assume settings in EXP have the GPS at the stern (lets say 16m from the bow). So when the mark is pinged its at the bow - 16m further forward at the current HDG (or COG)?
Once both marks are pinged, then I assume EXP calculates the 'distance to the line' as the distance straight ahead, not perpendicular to the line - is it based on HDG or COG?
Would be grateful to understand the inputs and geometry for peace of mind please