Google-sheets – How to turn a list of comma separated values into an array

Use JOIN subject to FILTER by ISBLANK. For the example spreadsheet below, the command

=JOIN(", ", FILTER(A1:A6, ISBLANK(B1:B6)))

returns "Robert, Jay, Tim"

      A          B
1    Jon      attacked   
2    Robert     
3    Grace    attacked  
4    Jay        
5    Tim        
6    Shog     attacked  

You need to split the content of cells, then do the math (using arrayformula) and finally join again:

=join(char(10), arrayformula(24*(split(D26, char(10))-split(C26, char(10)))))

Here char(10) is the "new line" control character.

The above will preserve the format of the original cells (e.g., time will remain time). Note that the final result (after join) is just a text string, which cell formatting will not change. If you need the result to be formatted as a number, do it explicitly with value:

=join(char(10), arrayformula(24*value(split(D26, char(10))-split(C26, char(10)))))

Remark. Putting two values in one cell is generally a bad idea if you plan to continue calculating with them. It's mostly a thing we do with text or with final output.