this information was passed on to me after struggling with gas rating on a prepay card meter, hope it helps.
With the appliance to be checked operating at maximum rating setting
1. Press & release button A. This will wake up display.
Please wait..... will appear
Then in approx 10 seconds the amount of credit pre paid will also appear.
£7.54 ON
2. Press & release button A, this will then display amount owed.
£5.00 ON
Owed
At this stage ensure that ON is displayed in the Right Hand top corner.
If OFF is shown the meter is either out of credit or the anti-tamper device has been triggered. No gas will will flow.
3. Press and release button A. Static index is the displayed
Meter Index
0000.861 m3
Now have your stop watch ready.
4. Press and release button B and start stop watch at the same time.
Please wait..... appears again
Current index appears in approx 10 seconds.
Meter Index
000.871m3
Record this as your first reading.
5. After approx 60 seconds display will go out (hibernate) do nothing.
6. At 90 seconds wake up the display by repeating steps 1,2 & 3.
On exactly 2 minutes (120 seconds) since action 4. Press and release button B this will again show
Please wait..... In approx 10 seconds
Meter Index
0000.879m3 An updated index appears
Record this as your second index reading.
Calculate gas rate/heat input in normal manner for a metric meter.