Although the distribution of tubes is symmetrical in tube layout but an irregularity appears in the report.
There are three ways of determining the number of tubes/shell ID, Any of the followings will work,
In case you want to update the number of tubes, We recommend to add more tubes and then delete the unwanted tubes and avoid adding tubes in layout.
To add/remove tubes in the layout you can put desired value at Free Height in the Shell and Tube Heat Exchanger Properties<Bundle<Flow Section<Free Height,
Note: Do not press on Compute option again if you have added/removed the number of tubes else it will again evaluate the layout based on the values provided.