Can somebody tell me why these queries are written two different results and why?

desc employees;

employee_id number(6);
first_name varchar2(20)
last_name varchar2(25)
email varchar2(25)
phone_number number(10)
job_id number(4)
salary number(8,2)


1)select * from employees;

Buffrer-gets----165

2)select job_id,salary,email,first_name from employees

BUFFER_GETS----17

In second query it is accessing only few fields that's why it has accessed only few blocks, but oracle normal does block wise read not row or column wise read , so why difference has come.