To fix the grand total calculation, we add another step.
This step loop through all row to find the min and max of each value.
These min and max are then used by the grand total.

Patch by Linagora

Change-Id: If3200840764d0ad9cb63231ac9f67b5d5ed197f1
Reviewed-on: https://gerrit.libreoffice.org/42042Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>