If you had been in the pool and had your full 5Nd already the 1st block was based on pool HR of 48.35PH, the 2nd on 55.45PH, and the 3rd on 58.01PH. You have to remember that the 5Nd works in both directions so your estimate may have been higher

I was just using the values as listed on minergain - which I believe he takes into account the hash rate at the time the block is found.