Hmm, whats that "Warning" about maximum 500mA? (Can"t read it all )
Can"t we use a 1A USB adapter?
Reading here it says "….. enough current ~700mA ….."
That warning is most likely pointing out that the maximum current ONE internal usb port on a computer can provide is 500mA, and that you sould use a more powerful external source, such as a 1A adapter as you say.
It"s always good to buy a power source with a higher current rating than that"s needed, this way the power supply won"t fail or generate too much heat.
It"s the Voltage you have to be careful with, a higher voltage can fry your device fairly quickly. Never choose a power supply with a different voltage.