We multiply the apriori probability with a factor to take capacity into
account:
P *= 1 - 1 / [1 + exp(-(amount - cutoff)/smearing)]
The factor is a function value between 1 (small amount) and 0 (high
amount). The zero limit may not be reached exactly depending on the
smearing and cutoff combination. The function is a logistic function
mirrored about the y-axis. The cutoff determines the amount at which a
significant reduction in probability takes place and the smearing
parameter defines how smooth the transition from 1 to 0 is. Both, the
cutoff and smearing parameters are defined in terms of fixed fractions
of the capacity.