Some models, the 460DA, 440EB,450EB, 450DA, among others, have the fuel deck fill plate located at about the same elevation as the entry to the tanks at the other end of the fuel fill hose. Diesel fuel foams as it fills so the propensity is to be adding fuel at a faster rate than the foam bubbles can dissipate and you may get a spill out of the fuel vent or even out of the fill deck plate.
Since this is a product of the boat's design, there isn't anything to fix, but you can do some things to avoid the spills: learn the sound of filling the tanks.....when the foam gets to the tank inlet, the sound changes, so slow down or stop and let the foam dissipate; just slow down; there is a whistle you can get for the vent line that stops sounding when the tanks vent gets close to full (these things are irritatingly loud and you might draw a bunch of looky-lou's when you use one; Parker has offered a fuel return valve for the vent line that prevents overflows. You should also check your vent lines to be sure they are clear and run consistently up-hill to t he vent fitting or that they have a spot in the ose near the outlet secured above both the tank outlet and the vent fitting on the side of the hull.