howto use the attribute of "Access-Period"

I set the value to 3600, but it says [sql] expand: SELECT id, username, attribute, value, op FROM radcheck WHERE username = '%{SQL-User-Name}' ORDER BY id -> SELECT id, username, attribute, value, op FROM radcheck WHERE username = 'test' ORDER BY id rlm_sql: Failed to create the pair: Invalid octet string "3600" for attribute name "Access-Period" -- Spacelee