Since it's alpha/beta state though--and an unofficial volunteer contribution--it's a semi-finished tool...
For example, some of the field labels might not mean what you think they would.
If you play with the calc a bit though, it's pretty easy to figure out what's going on.
...
Sorry, but I have no idea how to translate the data given by the wallet into what that calculator requires to proceed. Also, I have yet to find stats on PoS difficulty (the difficulty for mining is no problem) without which the whole exercise is moot.
The way I see it, estimating the probability of receiving a stake should depend only on the following:
# of coins
age of each coin (or average age of all coins)
PoS difficulty
Where do inputs and # of coins per input and age of transaction come into play?