Your LPG tank gauge gives you an indication of the amount of LPG in the tank rather than an exact measurement.
The reading can be affected by temperature. LPG expands when it gets warmer and contracts when temperatures fall. As a result, you may sometimes see the gauge move more than expected even though you haven't used an unusual amount of LPG. It's also why your bulk LPG tank will only ever be filled to 85% so room is left for the gas to expand in high temperatures.
If the gauge appears to be dropping consistently faster than expected, however, it's worth looking at your LPG usage, checking that your heating system is working efficiently, and checking for signs of a leak.
If you're using more LPG than usual, read our blog as to why your LPG consumption may have increased.