Voltage regulator minimum input voltage
On a linear regulator you can not work with the same voltage at input and output.
Basically inside the component there are transitors that are not perfect transistors, because they have a resistance when the current flow through them, and this resistance leads to a loss of voltage in the component.
It is called the drop out voltage.

The maximum output voltage you can have with a given component and a given input voltage is :
Vout = Vin - Vdropout.

In your datasheet it is wierdly written since Vin is refered at the drop out voltage. The datasheet say the min Vi is 8V, meaning the drop out voltage is actually 3V. Meaning if you put 5V at the input you won't have more than 2V at the output. Then you have to use your jumpers.