Tradition. They are metaphors used to illustrate.

The bank loans the person 900GP by essentially putting themselves into a "900GP" debt with that person--what this means to the parties involved depends on the value people associate with 900GP in that society. The bank still definitely owes that person 900GP, but since the bank is supposedly reputable (i.e., people trust that it will make due on its promises if the person comes calling for his gold) the person taking the loan is willing to in turn put himself into debt with his employees: Hi everyone, I do not really get how Reserve requirements work. It is 10 per cent is it meant that I need to keep 10 percent of the total liabilities which is 300GP? but, this would only work in the case where we are sure that the person would not withdrawn all money right away, am I right? Because if loan borrowed are to be withdrawn right away, which is gold in this case. The bank would not have enough gold to pay the person. even if it kept the within the 10per cent.

AD4