A null value will return as '0'.
Meaning that, if a Player enters a value of 0, it will be treated as non-number value has been entered.
Other than that, the system can differentiate between number and anything (sign, symbol, etc).
Instruction:
1. Just enter any value (via chat) and it will show you a message whether you have entered a number or not.
Examples:
1234 is acceptable
1001 is acceptable
hey there is not acceptable
i1a2m is not acceptable
huhuh1003 is not acceptable
1003hello1002 will only accept the values before "hello"
0000000089 is acceptable (returned value is 89)