Editing the column alignment from the "Column" tab under properties does not change the alignment of a 'number type column'. This includes using the left alignment icon on the toolbar, as well as using the customization wizard (that appears when you click the ellipses next to the "Styles" property).
You are unable to edit the column alignment.
This is a known issue that has been logged to be included in a future fix.
In the meantime if you would like to change the column alignment for number data types, edit these styles with the left alignment icon or the Styles wizard under the "Body" properties tab instead of the "Column" properties tab.