Calculated measure or member?

I’m trying to create a simple table showing open issues over time for three issue types - bugs, action items, and project risks.

One of those issue types - bugs - needs to be filtered to show customer facing bugs only. In Jira this is done by filtering by a custom field value of > 0 (it’s a numeric field).

Intuitively, I think that I should be using a calculated member in the issue type dimension, but other posts I’ve seen here suggest creating a user defined measure in measures.

What is the correct approach? Should I somehow modify the open issues measure to count / filter on bugs with a custom field numeric value? (The custom field also exists as a dimension but I don’t think that’s the way to go here)

The table should look something like the below screenshot