this is what the ben 10 wiki says about it: What triggered the Recalibration Mode is unknown, but it is speculated that since the Omnitrix bonded with Ben's DNA again, and since Ben was five years older than he was before, the Omnitrix changed to fit Ben's age. Dwayne McDuffy said it recalibrated due to his matureness . The abilities of his old aliens were recognized by the Omnitrix and therefore "upgraded" as well, bringing 10 new aliens with the same abilities as the old aliens.