When calculating a pipe schematic, the reports will show the lengths for each considered section.
Twin Pipe Network
If your pipe schematic is composed wholly of twin pipe
Your pipe report will show the combined flow and return length of the pipe.
Combined Twin pipe, flow and return network
If your schematic is composed of a mixture of flow, return and twin pipe
Pipe notes will show flow pipe numbers in black, and return pipe numbers in red. Twin pipe is reflected in both reports.