I seemed to notice the Expected per block value changes quite frequently and seems to be tied directly to the total hashrate of the Bitminter Pool. However today I noticed this value was cut down dramatically. Yesterday it was around 0.00431987, but as you can see today another "0" as sneaked in between the decimal and the numbers I care about. (The difficulty hasn't changed since yesterday)
So I ask you...can you help me understand what determines this Expected per block value? And possibly why it was cut down so much?

Thanks in advance for you taking the time to help explain this subject to me. I am still very new to the bitcoin scene, but I am trying to flood my brain with knowledge on this subject. So please help if you can and feel up to it!

-Byteme
http://i967.photobucket.com/albums/ae152/stonedfreedom/wtf_zps56388fa9.png