Why actual quantity isn't calculated?

The actual quantity won't be calculated if the unit of measure for planned resource is different from the unit of measure of actual project costs.

For instance, if the unit of measurement for a planed resource is Currency and unit of measurement for project costs is Hours, then the actual quantity isn't calculated.

In scenarios as mentioned above, a warning message appears. To resolve the warning, you can delete the planned resource and assign a resource with the unit of measure as that of actual project costs.