Hi Antonio,
When using Lumira Desktop to create a Donut Chart and you highlight a slice in the Compose room, it will automatically show the title of the slice followed by a "/" and then the number of slices which made up the rest of the donut. So the value "6" represents the "other" slices.
You can remove this by going into the Visualization Properties in the Compose room on the right hand side, selecting "Slice" from the drop down menu and then removing the "Show Name" checkmark.
Use the Text import on the left hand side to layer your own title/messaging.
regards,
K