What did Shen mean by 30 years?
Most fans believe that Shen attacked the panda village and was exiled for 30 years ago, but now few believe that he began to use fireworks as a weapon 30 years ago and years before he attacked the panda village and was exiled, since in Kung Fu Panda 3 Mr. Ping mentioned that he raised Po for 20 years before Mr. Ping told him he was adopted and in Secrets of the Scroll he was a teenager 10 years ago..
But it's not even revealed that Shen began to use fireworks as a weapon years before or it was 20 years ago he attacked the panda village and was exiled.