Okay, It would take a Basic level 50 Druddigon, Just standard Druddigon.
Now it would add all of the EV's your Druddigon has to the Level 50 Druddigon, Followed by your IV's and Nature plus your moveset,
Molding its stats to what your Druddigon would be if you Rare Candy Leveled it from there on in retrospect.
So it basically just says, " Hmm, what would this thing's stats be if he leveled it with Rare Candies all the way to level 50? "
Or they have to lower your level, and they Add your IV's Ev's and Nature to affect your stats.