It contains the International Bank Account Number (IBAN) according ISO 13616. For the Czech Republic IBAN has the format CZkkbbbbrrrrrruuuuuuuuuu, where kk are check digits, bbbb is a 4-digits bank code, rrrrrr is the first part and uuuuuuuuuu is the second part of an account number (all with leading zeroes). At the end are 10 spaces. (There are no spaces inside, spaces are sometimes added only for better readability.)