Your ability to alter your spell of choice is greater than expected.
Choose: A spell of 3rd level or below.
Benefit: When you use the chosen spell with a metamagic feat, it uses up a spell slot one level lower than it normally would.
It is likely that the same clarification Jason B. made for the Magical Lineage trait (see [Source] link below) also applies to this trait but until he or someone else at Paizo states as such, consider the following just our assumption:
"This trait was never intended as a way for you to actually lower a spell's level. It was put in to allow you to reduce the increase from a metamagic feat. So, no unlimited magic missiles. I will see to it that the language of this ability is clarified soon and I will get this added to the FAQ."