multi numeric alert - how to pull out values in email

hello support, 

I am testing "Custom SQL Alert - Multiple Numeric Return" with following SQL 

SELECT
CONVERT(VARCHAR,a.session_id) AS session_id, CONVERT(VARCHAR,DATEDIFF(SS, a.start_time, CURRENT_TIMESTAMP)) AS duration_in_seconds
FROM sys.dm_exec_requests a
CROSS APPLY sys.dm_exec_sql_text(a.sql_handle) b
WHERE a.status <> 'background'
AND a.database_id <> 1
AND DATEDIFF(SS, a.start_time, CURRENT_TIMESTAMP) > 50

It output session_id and its duration_in_seconds. When i test this alert with my current email template, it does not return me these values in email 

this is my current template of email 

Alerting At: [=alert.executionTime]
Alert Type: [=alert.type]
Alert Status: [=alert.status.value]
Alerting For: [=database.name]

What variable should I  use to take this output out in email? 

Thanks