How to tacle Self Service receivers' receiving errors ending up to GL

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We experience somewhat often that users creating expense receipts in self-service ("My receipts") receive a wrong amount (usually bigger than was supposed to. This receipt creates an entry to our GL and sometimes these errors are significant. E.g let's say the correct amount is 1000 EUR, but user makes a typing error and types 1000000 and this creates an entry to our GL.

How do you others' tacle this kind of issues? We try to monitor the receipts on a regular basis to notice any errors/over-receiving, but I would love to know how you others manage to avoid this kind of issues or what is your routine to correct these.