Left Join in Mysql?

Left Join in Mysql?

This is my first Table.

Then the second one is

Now I am trying to do Left join like this
SELECT t1.StackID FROM t1 LEFT JOIN t2 on t1.StackID=t2.StackID
Output

I am confused here, Is this the correct output? Is not this supposed to
return only the 5 rows which is present in left side table.