The first part of this keyword serves a similar role as the BY statement, defining an aggregation floor at the granularity level of the specified attribute. But the keyword also overrides all attributes in all other dimensions—keeping them from having any affect on the metric.
ALL IN ALL OTHER DIMENSIONS can be abbreviated as "All Other."
SELECT … BY … ALL IN ALL OTHER DIMENSIONS
SELECT metric BY attribute ALL IN ALL OTHER DIMENSIONS
SELECT SUM(Resolution_time) BY Quarter ALL IN ALL OTHER DIMENSIONS