Unexpected behavior when reporting on Call Duration

Hello,

I'm trying to see the total amount of time spent on a calls for each given call reason. The call reason is calculated using the tags on the call.

When calculating the total number of calls for each call reason, I can see a chart with each call reason showing the total number of calls for that reason as a bar next to it. However, when I change the metric from SUM of D_Count([Inbound Calls]) to my custom metric (SUM of INTEGER([Call Duration]), instead of showing the total duration by reason, it shows the total duration for all reasons next to each reason.

Oddly enough, when I exclude reasons in the column section or through filtering, the total on all sections updates to exclude the given reason duration total.

How do I go about showing only the duration time for each specific reason rather than the total for all reasons on each bar?