There are two types of meter display, They are mechanical and digital.
You read both in the same way.
One unit (on the black part) is 1000 liters.
So the image below reads:
Twelve million three hundred and forty five thousand liters,
Or
Twelve thousand three hundred and forty five units.
Your water company will usually only bill you for the units and not the decimals.

How to do a Flow test.
Mechanical meter.
Mechanical meters have an analog display like the mileage counter on a car, They can not record unless water passes through them.
First ensure no water is being used in your property,
Take a note of the meter reading from the meter,
Leave the property for a minimum of 4 Hours,
Then re-check the reading on the meter,
If the meter reading has moved during the flow test period and you are sure no water was being used you have a leak somewhere.
Do the same test again but this time Turn the stop tap off inside you property.
Take a note of the meter reading from your meter,
Leave the supply switched off for a minimum of 4 Hours,
When you return to your property re-check the reading on the meter,
If the meter reading has moved during the flow test period you have a leak between the meter and the stop tap.
Contact your water supplier to advise of the fault.
Digital meter.
Digital water meters have a digital display like a calculator .Although usually very accurate they can sometimes go wrong.
Typical problems are:
Flat battery, The display will be blank,
Loose earth wire, Can cause the meter to miss record usage,
Mechanical appliance too close to pipe work and vibrating the meter, Can cause the meter to miss record usage,
They can also sometimes record usage without water passing through them.
Always check where your internal stop tap is and it is in working order,
If not then contact a plumber to get it repaired,
First turn you taps off and ensure no water is being used in your property,
Turn off the stop tap inside your property,
Take a note of the meter reading from your meter,
Leave the supply switched off for a minimum of 4 Hours,
Then re-check the reading on the meter,
If the meter reading has moved during the flow test period you meter is recording without flow.
Contact you water supplier to inform them of the fault.
Meter Accuracy Test
This test is the same for all types of meter.
First of all make sure no water is being used in your property,
Take a note of the meter reading on the meter,
Take a container that has a measurement scale on or one that you know how much water it holds,
Fill it with water from the tap or shower,
Check the meter has only moved the same amount of decimal places as liters you have taken from the tap or shower.
If after doing this test you think your meter is not recording correctly contact your water supplier.