This summary is not the rule. The rule text controls.
Parties in a lawsuit can agree to use fewer jurors than the law normally requires. Instead of the usual number of jurors, both sides can decide ahead of time to use a smaller jury.
The parties can also agree that the verdict does not need to be unanimous. For example, they could agree that a verdict only needs to be reached by a certain majority of the jurors, rather than requiring every single juror to agree.
This gives people involved in a case some flexibility. If both sides are comfortable with a smaller jury or a majority decision instead of a unanimous one, they can set that up before the trial happens.