User blog comment:FairyRaven/Fairy Tail Chapter 387: Tartarus Arc, Part 4: Father and Son, Review and Commentary/@comment-2214433-20140606093311/@comment-4164634-20140606123131

well, the only way to know is if we ask Mashima himself on twitter. I think it could be twenty cause I highly doubt the Magic Council would build that many (let alone have the jewels for it)