Maybe if number equals 0, for other numbers the uid becomes part of the password.
Hopefully the write function does a better job.
uint8_t start = (number *7) + 2; // Figure out WRONG starting position
for ( uint8_t i = 0; i < 4; i++ ) { // Loop 4 times to get the 4 Bytes
storedCard[i] = EEPROM.read(start + i); // Assign values read from EEPROM to array
storedPass[i] = EEPROM.read(start + i + 4);
}
}