form_validation error messages

[eluser]Skuja[/eluser]
Just wanted to note that I find these error messages inadequate:

Code:

$lang['is_natural']        = "The %s field must contain only positive numbers.";
$lang['is_natural_no_zero']    = "The %s field must contain a number greater than zero.";

Because natural number is non-negative integer not just any positive number.