Phone number format

PractiScore Tools PractiScore.Com, the Website
1

What is the correct phone number format? Does it accept format of individual countries or should I ignore it if I am from outside of US?

2

I just tested a registration with different country codes and they all worked fine.

3

Hi,

so how do I enter here:

phone number in a format such as:
+421 903 123 456
or
0903 123 456

Do I have to change anything in my account/profile?