Dynamic groups can be recalculated apart from whatever interval is set in the group definition. The recalculation interval in the group definition is a relative value based on the last update time, so initiating a recalculation manually will not conflict or interfere with the normal recalculation; it simply proceeds after the specified amount of times elapses.
Click the Inventory tab in the top menu.
In the Groups menu on the left, click the Dynagroup Definitions link.
In the list of dynagroups, select the row of the dynagroup definition to calculate.
Click the Recalculate button at the bottom of the table.