Cheque number from SOE Report

I am trying to derive Cheque number from SOE Report (Assignment -->Other SOE Report ) for a Canada employee.

SOE report  results shows a cheque number #40684,assignment_action_id = 4230309645

 

I used the following query

select assignment_action_id, serial_number from pay_assignment_actions

        where assignment_action_id = 4230309645;

 

But serial_number is NULL.

I looked for various notes and as per that serial_number should store the cheque number.

 

From diagnostics-->Examine also serial number is NULL.

 

When I try to back track by

select *from PAY_ASSIGNMENT_ACTIONS where serial_number=’40684';

I get a different assignment_action_id #4230310898.