Split streams and runtime variables

Suppose you are planning to develop a gas field, and intend to send part of the produced gas to a Gas Liquefaction Plant, according to the following rule:

While the cumulative Gas production is less than 10 Billion Standard Cubic Feet the percentage of gas used for liquefaction is 20%. Then the percentage is higher: 30% until reaching the 25 Billion Standard Cubic Feet of cumulative production, and 40% afterwards.

The following movie illustrates how this can be easily modeled by the combined use of the Split Streams functionality and Runtime Variables.