Waiting Events by Segment (4280503)

Spotlight uses below query to collect data.

SELECT object_name, VALUE waits, statistic_name
    FROM v$segment_statistics
   WHERE     statistic_name IN (SELECT DISTINCT seg_stat
                                  FROM quest_soo_event_categories
                                 WHERE     NAME = 'db file sequential read'
                                       AND seg_stat IS NOT NULL)
         AND VALUE > 0
ORDER BY waits DESC;

(You will need to use the same Oracle user as you are using in Spotlight for this to work).
We get the data from v$segment_statistics for physical reads -

 It has most likely to do with the table being taken out of the shared pool - probably overnight when no one used the table for a long time. Please check out below link.

http://docs.oracle.com/cd/E16655_01/appdev.121/e17602/d_shared_pool.htm

Otherwise you could ask Oracle for more details on the view - the documentation doesn't say much about it -

http://docs.oracle.com/cd/E16655_01/server.121/e17615/refrn30220.htm