For the first part you should be able to use Col Sum with If (you don't need If if you are fine that all cells have values)
If(Row() == Col Max(Row(), :Counter),
Col Sum(1, :Counter)
,
.
);
other option could be to use Col Number(:Counter, :Counter) (add similar if statement if you need it).
For the other question, I would most likely create new formula column with
In Hours(:"Day/night hours"n)
and then change the format (you could also multiply by 60*60 (In hours does this, it converts hours to seconds), JMP datetimes are in seconds so you want to convert your hours to seconds and let JMP handle the formatting from that)
![jthi_1-1704745410479.png jthi_1-1704745410479.png](https://community.jmp.com/t5/image/serverpage/image-id/60229i7709661B27D318CE/image-size/large?v=v2&px=999)
You can also change the format to Best to see the "real" underlying value (seconds).
-Jarmo