Its simple. Because on those short blocks, the block was solved before you submit even one share. Check the amount of shares they were submitted, its less than 300 shares. 1641 people were mining at that time, the block was solved before everyone submitted their shares!
ok, this may be the reason
however this pool should be PPLNS and I understand PPLNS means that when block is found you will look at last N (don't know the exact number) shares and distribute payouts among miners contributed to them proportionally to their contribution.
So also during short round like 10000 shares if N is e.g. 500000 you should recieve your payout even if you didn't have shares in this last 10000
(
http://ltc.kattare.com/about.php)
Therefore this means that this pool is rather RBPPS based???