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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
Duplicate issue
And the problem why it happens is explained in the post below yours. Closing this one.
Added the text written by dfhwze to the kata's description and a couple of examples to see what that means.