I believe it is something to do with the total amperage (current) available. Standard household circuits in Aus carry 10 amps.
You have to work out the total current of all your devices and make sure they dont exceed 10 amps
The formula is amps = power/voltage.
e.g. A 2400W device at 240V would draw 10 amps (at full power). A 60W globe would draw 1/4 Amp.
Your computer + screen would probably draw up to 5 amps depending on the power supply (usually around 400W). Youd also need to know the power drawn the fridge but there would be a label somewhere. but dont forget the compressor isnt running the whole time anyway. The wattage of the Sunbeam should be printed somewhere.
You need to think about all these devices operating at the same time for there to be a concern. Youll know youve gone to far when the fuse/safety switch goes off.