The circuit shown will produce a dot display. Connecting pin 9 to +V, the display will become a bar of LEDs.
The LED brightness is controlled by R1. Reducing the value (minimum 330 ohms) increases the brightness. In dot mode this is not a problem, but in bar mode, potentially all the LEDs could come on so it is advised at voltages of 9v and above, not to reduce R1 below 1K. The IC package will get hot if you do so take care.
This can be made very sensitive by increasing VR1 to 100K. Internally the resistor chain is made up of 10 x 1K resistors so to calculate the voltage range you can use the following:
Vmax = Vin x (10K / (VR1 +10K)
so when VR1 = 100K and the supply = 12v the range will be
Vmax = 12 x (10K / 110K) = 1.1v or 110mV per LED step.