So, for example, if I start a campaign as a just-hatched White Dragon Wyrmling (3 dragon HD and a +2 LA), and then gain 5000 XP so I can advance to ECL 6, and I choose to take a fourth dragon HD, do I get an attribute bonus? Or do I have to wait until I've gained four dragon HD beyond the 3d6 that the WDW starts with? What about a Brass wyrmling that starts with 4 dragon HD the moment it hatches?
I read slowly and am terribly distraction-prone. I'd rather get an answer right now than go looking for where it might have already been given.