Pool luck (1 day, 7 days, 30 days): 51%, 98%, 95%. And since we found 10 blocks today I can guess that the 1 day luck is finding 20 blocks. Is that correct?
The same for the weekly and monthly luck:
Luck = shares calculated / blocks found / difficulty * 100
To make it easier to calculate with the difficulty changing from time to time Slush probably calculates the % for each round and then just averages the % for the period i.e.
round luck = shares / difficulty * 100
There is small mistake introduced at each difficulty change, because part of the shares are against the old difficulty, but it can be ignored and not worth the complication of calculations