I am a bit confused about some supposedly basic electronics concepts :/ (I kind of have an answer but just want to confirm)

So let's say I have got this setup:

• A 13A 220V mains socket
• A 13A powerstrip connected to the above socket
• Two 60W 5V USB chargers, such as this http://www.amazon.com/gp/product/B00P936188

Question: If I plug the 2 chargers and fully utilize them (connect all ports to charging iPads), am I overloading the socket?

Simple addition of the amperage is:

12A + 12A = 24A > 13A, so I am overlaoding

However, the wattage is just 60W so maybe the correct way to calculate it is:

Power = Current * Voltage
Current = 60 / 220 = 0.27A

So the input current is actually just 0.27A so I can actually safely connect as many as 13 / 0.27 = 48 of those chargers to the same mains without problems. The 2A is provided by the transformer inside the charger and doesn't concern the mains circuit.

Which one is the correct interpretation?