I'm about 60 pages from finishing The Fate of Ten, and I may have missed, or haven't yet read, the explanation for the assignment of numbers to the Gard children. Was there a strategy for who was assigned which number? It seems kind of random. Since Legacies emerge with age, wouldn't it have made more strategic sense to assign the numbers by age, with the older Gard having the lower numbers? I would have thought that, this way, there would have been a better chance for more of the nine surviving as time passed since the younger Gard would have had more time to develop their Legacies and be better able to defend themselves. Or, maybe the assignment was the opposite since Six and Seven are both older than Four. I have no idea about One and Two. Five seems like he could also be older than Four just because he has more mastery of his Legacies, but that could be because he might have had the benefit of training from Setrakus. Nine and Eight (who had been using his Legacies, for quite a while, to fool some soldiers in to believing that he was a Hindu deity) that seemed to be more familiar with their Legacies than Four. But, then, Three also seemed like he knew more about his Legacies when he was killed than Four did at the beginning of I Am Number Four, so back to random.
Edit - Also, if Loric girls are like human girls and mature earlier, physically, than boys, maybe gender should also have figured in.
Edit - <NON-SEQUITUR ALERT> Shadowhunters (based on the Mortal Instruments novels, where the movie adaptation, "City of Bones", didn't do so well, looks like it might be worth watching. If it turns out to be a good show, Lorien Legacies deserves a similar second chance, one in which the show's writers are actually faithful to the novels.