fixVersion is set to the version.affectedVersion is set to the version.curl --location --request GET '/rest/api/3/version//relatedIssueCounts'{"customFieldUsage":[{"customFieldId":10000,"fieldName":"Field1","issueCountWithVersionInCustomField":2},{"customFieldId":10010,"fieldName":"Field2","issueCountWithVersionInCustomField":3}],"issueCountWithCustomFieldsShowingVersion":54,"issuesAffectedCount":101,"issuesFixedCount":23,"self":"https://your-domain.atlassian.net/rest/api/3/version/10000"}