Board Thread:Dragon City Gameplay Questions & Answers/@comment-24577379-20140222033859/@comment-24290554-20140222065856

The numbers you see on the dragons mean the parents' level requirement. Both parents need to be at least at level 10 in order to get a centipede dragon.

As for the free dragons, sometimes it takes some time for the games to read and relay. What I can suggest here is you   clear the cache then click the Dragon City island from Social Wars. Once the game is loaded collect the egg. If it is still not working, continue playing Social Wars for some time. From my personal experience I do not have problem with the Social Wars but with Social Empires. I got the Butterfly Dragon when I reached level 23.