Look at the ranges on each of those toe and heel reference points. smaller range on toe keeps the boot centerline closer to the mark on the ski.
Think of it this way, toe marked every 25 mm would be 250, 275 and 300.
If toe piece was set at say 275 in this case and the sole length is 282, there is a 7mm difference which I think would put the line 3.5mm (assume 1/2 the difference) behind of the line. The heel just is where it needs to be to allow for forward pressure to be adjusted properly.
If set at 300, the toe would be 18 mm off so the toe would be 9mm ahead of the line.
If the toe range was cut to say 4 mm between setting points you'll keep the boot line closer to the line on the ski.
Again the heel is sort of an afterthought. The range is a good place to start, but not cast in stone --although I'd have guessed it would be marked closer to the toe measure.