Smart meter gas readings

I have a smart meter fitted by EON. Previous gas readings have been 234 in December 2018, 481 in February 2019. I went to take a reading today (24-March-2019) and the gas reading now says 6446.
Clearly it’s been a cold month but I surely haven’t used THAT much gas!
The electricity readings have been 1136, then 1837 and today 2123 so that seems quite plausible.
Have units of measure changed on gas usage in the past month? I wonder if the reading now goes to an extra decimal place but I took the readings in the same way last month when it showed 481