Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Functions.php
public static function n($value = null)
    {
        while (is_array($value)) {
            $value = array_shift($value);
        }

        switch (gettype($value)) {
            case 'double':
            case 'float':
            case 'integer':
                return $value;
            case 'boolean':
                return (int) $value;
            case 'string':
                //    Errors
                if ((strlen($value) > 0) && ($value[0] == '#')) {
                    return $value;
                }

                break;
        }

        return 0;
    }
public static function n($value = null)
    {
        while (is_array($value)) {
            $value = array_shift($value);
        }

        switch (gettype($value)) {
            case 'double':
            case 'float':
            case 'integer':
                return $value;
            case 'boolean':
                return (int) $value;
            case 'string':
                //    Errors
                if ((strlen($value) > 0) && ($value[0] == '#')) {
                    return $value;
                }

                break;
        }

        return 0;
    }
N.

Returns a value converted to a number

@param null|mixed $value The value you want converted

@return number N converts values listed in the following table
If value is or refers to N returns
A number            That number
A date                The serial number of that date
TRUE                1
FALSE                0
An error value        The error value
Anything else        0