The former Bodo-Glimt striker joined Milan in the final days of the summer market and is already off the mark for his new club.
Corvino told Gazzetta dello Sport: "I wanted him at Lecce, he's a complete player.
"I needed a quality winger, he struck me and I offered €2 million but then Milan came. I am pleased that Jann Petter has seized such an important opportunity for his career. He is already a specialist in the role, he is fast and complete as well as having great physical strength.
"Playing at high levels, alongside champions like (Zlatan) Ibrahimovic, can only give him the opportunity to learn: from the information I have gathered in recent months he already has great personality."