Hi,
One easy way is to use If condition.
Are you trying to show like this table?
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Use a dax like this, Similarily for each value. But this way cannot be used if there are multiple values.
Count C = IF('29Aug'[Category1]=="C"|| '29Aug'[Category2]=="C"||'29Aug'[Category3]=="C",1,0)
Try it out.