A general electronics rule is that the device will draw the current it needs and the voltage you give it. So the current is not what you need to worry about cause it will draw 0.3A even if the power supply is rated at 1A. the power supply rating is the absolute maximum current it can provide to a device. Voltage on the other hand needs to be regulated. If you give your device 24v it will take 24volts and explode and kill several people.
However some devices or components like LED's need both voltage and current regulated. I hope I am correct