There are two fields in "calls" called "duration_hours" and "duration_minutes".
If you need to compound them into one (with total minutes, for example), you can create a new custom field for it, and use an on-save workflow to calculate that field. This way the data will be prepared so the Report is easier to build.
My SuiteCRM In-depth blog. Thank you for always stating your SuiteCRM version, checking your logs, reading the Docs, and searching before you ask!
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