Spider Order By column[datatime] limit 5 returns 3 rows

when quering with innodb table:
SELECT *
FROM phms_family
WHERE region_code LIKE "%510411106%"
AND region = 510411
AND delete_status != 1
ORDER BY update_date LIMIT 5 OFFSET 1
return 5 rows;
but spider table ,return 3 rows;
update_date is a datatime column, with null field.