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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.
The first value in that error message is your wrong answer. Not a kata issue.
But it does not say that 8161 is an expected answer, does it?