CDF is a much better number to look at than "luck" which can vary from pool to pool on what they even mean by the word. The CDF you can think of as the probability a block would have been found given the current difficulty and number of shares that have been submitted to the pool.
Right now, the pool CDF is 62.73%. So given the amount of work done since the last block, the pool would have found the block by now 62.73% of the time.
50% CDF is the median (half of all blocks found should be < 50% and half > 50% with a large enough sample size), 63.2% is the average.
Remember no matter how long the current round has been it has no effect on the odds of finding a block. The purpose of calculating and graphing things like the CDF of rounds is so the pool can be analyzed to be sure there's not something wrong with it.
When a round goes really long and has a CDF of 95%, it's annoying, but 5% of all blocks will end up at or higher than 95%. 1% of all blocks will end up at 99% or higher. But on the other hand, 5% will end up at 5% or lower and 1% will end up at 1% or lower.
Edit: Corrected typo and re-worded something for clarity.