OK so here is what I got:

Round 21628 Thru 21657 = 30 Rounds

Total Shares = 78149042396

All blocks solved at Difficulty - 2,621,404,453.06

2,621,404,453.06 * 30 = 78,642,133,591.8

So Total Shares - 78149042396/78,642,133,591.8 (Difficulty * 30) = x

x = .993729936189684

k=30, lambda=30, x=.993729936189684

RESULT = .5105800139110

OK! Now it's up to you to tell me/us what this number means  

Thanks