From Dragon Mania Legends Wiki
Dragon stats are the main formulas used to determine a Dragon's strength, productivity, and endurance. There are three categories for stats: Health, Attack, and Gold per Hour. While Gold per Hour stats are used to determine how much Gold a Dragon will produce each hour, Attack and Health stats are used to determine a Dragon's capabilities in battle before factoring in Elemental skills. Many Dragons will have identical base stats in one category. When this is the case, the Dragons will have the same stats when levels increase. This is not necessarily true of Attack, where Dragons may diverge into different leveling groups.
While the vast majority of Dragons possess stats, some Dragons do not fall into this category or their stats serve no purpose outside specific circumstances. Clan Dragons have no stats whatsoever, while Boss Dragons do not produce Gold, thus they have no Gold per Hour stat. In addition, Boss Dragons can not be used for battling nor leveled, thus their other two stats apply only when fighting against them on the Campaign Map.
The base stats are the values given to each stat when the Dragon is Level 1. In the case of Legendary Dragons, the base stat when one or both of its secondary Elements is awoken is the one that would be at Level 1, as these Elements can only be awoken at Level 20 and Level 30. Thus, the base stats for Legendaries vary in accordance to their number of Elements. The base stat of any Dragon can be viewed by following the Dragon Codex and reading any of Codex entries available there. These stats are based on its rarity and Elements.