Hi,
The 18.83mA you are looking for is the current through a 325 Ohm resistor with 6.12V
18.83mA = 6.12V
325Ohm
As you have an LED in series with the resistor you have to take into account the voltage drop of the LED.
For example, if the LED is a standard red one the voltage drop of the LED is approximately 1.7V
So:
Current = 6.12-1.7 = 13.6mA
325
Depending on the type of LED you are using the current will be different, hence the 11.2mA you are reading.
Also to measure the voltage of your potential divider with the multimeter,
Connect the black COM of the multimeter to ground, and connect the red V lead to the junction between the two resistors.
Dean