The program you have is not COMPSELECT then. It sounds like a blend of portions of the COMPSELECT ported to BASIC and blended with KEDS (Kodak Emulsion Design System). KEDS was (is?) far more comprehensive in capabilit as it produces the code to run the process control equipment directly along with the model and error messages.
All of this was to be replaces by ESP (Emulsion Scaling Program).
I build my electrodes from Silver "wire" as shown in the book, and plate them as described. But using them in critical situations requires a bridge of neutral salts to prevent Cl contamination of the make. The double junction electrode "leaks" Cl enough to disturb measurements. The book shows examples of a bridge.
There is so much more to this that you are missing which I left out of the book as I did not want to get overly complex. You see, even what you have is a dumbded down version of what we used which was capable (in the end) of handling up to 60 segments, but generally handled 25. That was an average make, not 15.