Modifiers can be given an interval by adding '/x' to the end of the modifier. The intervals can be used to create Sources, Drains or Converters that produce or consume resources in burst at regular intervals. For example the interval 3/4 for the uptput of a Source indicates the source will produce 3 reosurces every 4 seconds. These resources are produced in a burst instead of at regular intervals. A source with an output modifier of 0.75 behaves differently.
Note that the slash seperating the modifier value from the interval is evaluated last by the tool. Thus the modifier '2D2-1/3D2+1' has a value of 2D2-1 and an interval of 3D2+1. You shoud read it as '(2D2-1)/(3D2+1)'.
Interval values can be random, you can use for example an interval of D6+2 to create an interval of between 3 and 8 seconds or turns.