The GATE column indicates whether the film gate dimension used in the calculation for that line is a Nominal value (60x60mm for a 6x6 format), or the true Actual value (56x56mm for 6x6). That tiny difference can make a substantial difference in the results.
Another example might be 4x5 sheet film, which is not actually 4-inches by 5-inches in size to begin with, and is even less once the actual image area is masked off by the film holder.
The tool itself is a personal creation by and for myself. It's been around since 2009 and was originally designed to create flash-to-subject distance tables that could be printed and stuck on my various cameras. Back then I had an old no-name electronic flash that had lost its calculator dial and I needed a replacement table. Later when I began using flashbulbs on a Graflex, it was perfect for those as well.
Since that time the tool has turned into sort of a Swiss Army knife of strange features, each of which I needed at some point in time and could not find another source for answers, and so got tossed into the eclectic mix.
Here's the main help screen for a better idea of what it (currently) does. It's an old-school Windows command line utility because it was originally intended just for me to get quick answers to my own questions. Although as such it does seem like a philosophically complementary fit for old-school analog photography in general...
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The earlier use in this thread for converting 6x9 focal lengths to equivalent 135 focal lengths was achieved by invoking the /efl option shown above, together with the /h option for data highlighting.
I had an earlier downloadable version of this utility in the Articles section of the old APUG, just for anyone who might like to play around with it. I think a small handful of members here might have looked at it. But there was quite a bit more interest from outside of APUG, since the articles themselves showed up in Google searches.
The above screen shows a much newer version than that older one. I was going to wait for Sean to get around to reworking the new Resources section (the Articles replacement forum), then upload this newer version there.
Ken