There is a database about department management with three tables.
Table head: This table seems to store information about the heads of departments. The columns include:
* head_id: A unique identifier for each head.
* name: The name of each head.
* born_state: The state where each head was born.
* age: The age of each head.
Table management: This table appears to store information about the management of departments. The columns include:
* department_id: A unique identifier for each department.
* head_id: A foreign key referencing the head_id column in the head table, indicating which head is responsible for managing the department.
* temporary_acting: A boolean flag indicating whether the head is temporarily acting as the manager of another department.
Table department: This table stores general information about the departments. The columns include:
* department_id: A unique identifier for each department.
* name: The name of each department.
* creation: The date when the department was created.
* ranking: The ranking of each department within the organization.
* budget_in_billions: The budget of each department in billions of dollars.
* num_employees: The number of employees in each department.

SELECT count(*) FROM head WHERE age  >  56
According to the database information, can you tell me what dose this SQL do?