Merge pull request #158 from Bernhard-Krop/error_with_code_11_using_check_digit_k

Solution for Issue: Error with Code 11 using check digit K

Author: casperbakker

src/Types/TypeCode11.php

@@ -91,7 +91,7 @@ private function getCheckDigitK(string $code): string
 
         $p = 1;
         $check = 0;
-        for ($i = strlen($code); $i >= 0; --$i) {
+        for ($i = (strlen($code) - 1); $i >= 0; --$i) {
             $digit = $code[$i];
             if ($digit == '-') {
                 $dval = 10;