A confounding variable is an extraneous variable that is related to your independent variable and might affect your dependent variable. In an ideal study, there will be no confounding variables.
For example, student accounts have a limit of $100 limit per day, while non-business accounts usually are limited to $500 withdrawals a day. For business accounts, the bank offers $1000 withdrawals in one day. Chase also offers customers a withdrawal limit of $1000 every 24 hours.
But, if you are using an ATM, there are daily withdrawal and cash dispensing limits and hence the amount you can get might be limited to your bank balance or the daily withdrawal limit. Usually this withdrawal limit is Rs. 25000 or Rs. 50000 depending on the bank and your account type.