Well you always have the total amount in dimension level by design, so the users are able to figure out how much the other depts combined measure amount is (total-dept01). There is no way around this, cubes overall sum is alwayd the same, no matter what categories are visible or not.
You could manually suppress all other depts. In case your depts can change over time (new ones), you could in your data source have the logic that all other depts that 01 has the dept-value of blank (or NULL). Then in the dimension's dept-level have the Inclusion property to be Suppress Blank Categories. Now you only see dept01, but overall sum is still altogether.
Cheers
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