When you level up ninja (in your case it's sakura) you raise stats ONLY for all form of that ninja. In your case it's all forms of Sakura. But when you level up any ninja you also level up your Bond Level, wich raise stats for all ninjas in current formation, but one level up gives only a little bit. For example o first screen you can see my Sakura Level. Those bonuses get only sakura. On second screen you can see my bond level. Those stats get all my ninjas in current formation. I hope you understand me)