Is my username apt?

I just started mining with Slush's yesterday.  For reference I just have an AntU1.  Here are my first few blocks (I went offline at 22152, power outage).

#           Block found at           Duration   Total shares    Your shares    Your BTC reward    Block #   Block value           Validity
22151    2014-05-29 08:40:41    0:31:01    1009492763    725                    0.00001673    303149    25.02545496    4 confirmations left
22150    2014-05-29 08:09:40    8:01:16    15694913790    10625            0.00001575    303145    25.03866986    confirmed
22149    2014-05-29 00:08:24    6:03:28    11813716997    2788                    0.00001739    303097    25.18944223    confirmed

So for 22149 I jumped into this round very late.  This is the first round I mined and my share ratio is at it's absolute lowest.  Yet the reward is at it's absolute highest.  How is this possible/fair?

To elaborate:  22149 was a 6 hour round, I mined for maybe the last two hours of it.  22150 and 22151 I mined beginning to end of round.  The ratio of (My Shares / Total Shares) for 22149 is staggeringly low compared to 22150 and 22151 - YET the reward for 22149 is higher.  I participated/did less work in the round I got the most reward in.

Can anyone explain this to me?