Connecting multiple Fairy lights in parallel to single power source
Fairy lights like the one in the question you link to are not series leds. They are all in parallel. A 5V supply for multiple series leds would not work. I answer how to get the forward voltage and current in that other question. 

Since your doing the math, simply adjust each string to reflect parallel leds. This is assuming you are replacing the resistor in the fairy light string, and let's assume 60 leds, at 3.2v at 10mA instead of 3.6v at 20mA, for longer life. You can adjust as you'd like, or if you measure the actual numbers.

R = ( V source - V forward ) / ( If * N leds )
R = (5 - 3.2 ) / (.01 * 60)
R = 1.8 / 0.6
R = 3 Ohms

This is per led string. 

Don't forget to get the right power.

P = V * I
P = 1.8 * 0.6
P = 1.08 Watts

A 2 watt resistor would be good for these values.

The 10 Amps are the max you should draw from your supply, so you take your actual total current draw, and subtract that from 10 Amps. If it's less, you're good.