How does Gary have 10 badges in the anime?

Question

In one episode, Gary tells Ash he's slow cause he's only about to get his 8th badge and Gary already has 10 badges. 10 badges? There are only 8 kanto gym leaders how does he have 10 badges but still need to battle Giovanni? Did he go to the Orange Islands or something? I don't normaly watch the anime but this kind of bugs me.

Answer 1

During his journey, Gary collected 10 Badges to compete in the Indigo Plateau Conference and Silver Conference. He won ten Badges in Kanto, of which he already had five by the twenty-fifth episode, and showed off the whole set in The Battle of the Badge (though he failed to gain an eleventh Badge in that episode when faced against Mewtwo). Of the eight Badges that Ash won, Gary only has three: A Boulder Badge, a Cascade Badge, and a Rainbow Badge. The other seven are unknown, but aside from the Earth Badge, he didn't get a Thunder Badge, Marsh Badge, Soul Badge, or Volcano Badge.

Source

That's what I found. I hope it answers your question.