Link to knowledge base on TOPN.
You can set the order to be applied. 0/FALSE/DESC – descending; 1/TRUE/ASC – ascending. https://info.enterprisedna.co/dax-function-guide/topn/
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Related content on dealing with categories
If this doesn’t help resolve the issue then like @LucaB72 already suggested provide a mock up PBIX file so members can better assist you.