The binomial distribution is a discrete distribution, that calculates the probability to get a number of successes in an experiment with n trials and p success probability.
The tool calculates the accumulate distribution function p(x<X), and the inverse distribution function. In the inverse distribution function, there is usually no X that meet the exact probability you enter. The tool will calculate the X that will generate distribution which is equal or bigger than the input probability but will calculate the probabilities for both X and X-1.
When the tool can't calculate the distribution or the density, using the binomial distribution if possible or normal approximation with μ = np and σ=√(np(1-p)) due to large sample size and/or a large number of successes, it will use the