Ever make a direct payment out of the till? For instance, for paying a supplier or giving to a charity? With the ‘in/out register’ feature you record this flawlessly. All cash transaction are registered with it.
When you add cash to the till you can register it wit this feature, e.g. replenishing your change. At the end of the day, you have the balance of these actions settled with the turnover, so no cash differences arise.