As a standard rule, the weight of gas your cylinder can hold should not be greater than the weight of the empty cylinder.
For example, if your gas cylinder weighs 12.5 kg when empty, then when filled with gas it should weigh 25 kg maximum.
If you have a cylinder that weighs 5 kg when empty then when full it should weigh a total of 10kg.
If you try to fill your cylinder beyond the recommended capacity, you risk cylinder explosion ? which can result to destruction and fatalities.