Multiprocess in a strong feature of the nodeeditor, that makes it possible to choose between different assignment strategies of the data. In other words a single datum of a numarray can be assigned to all members of another numarray or an objectlist. This is called long mode (1:n). In the so called short mode every element of a e.g. numarray matches to one element of another numarray (1:1). Here the shorter list defines the number of elements are processed.
Here is picture taken from a post of Max Smirnov  that shows the behavior: