diff --git a/app/Classes/Modules/Transactions/Processors/CheckStorageInvoiceTransactionProcessor.php b/app/Classes/Modules/Transactions/Processors/CheckStorageInvoiceTransactionProcessor.php
index 4d7cd3a4..85e88b59 100644
--- a/app/Classes/Modules/Transactions/Processors/CheckStorageInvoiceTransactionProcessor.php
+++ b/app/Classes/Modules/Transactions/Processors/CheckStorageInvoiceTransactionProcessor.php
@@ -238,6 +238,7 @@ class CheckStorageInvoiceTransactionProcessor
 
 
         $resultNumberOfDaysExceeded = $interval->days - $resultNumberOfDaysFree;
+        // to prevent negative number of days exceeded
         if($resultNumberOfDaysExceeded < 0){
             $resultNumberOfDaysExceeded = 0;
         }