I read about properties in org-mode tables, but either something is broken, or I cannot understand how to use them. Here's what I've tried:

:PROPERTIES:
:COLUMNS: %10item %10start(start){:} %10end(end){:} %10total(total)
:END:
|   | start |   end | total |
|---+-------+-------+-------|
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|   |  9:30 | 18:45 |  1:10 |
|---+-------+-------+-------|
|   |       |       |  7:10 |
#+TBLFM: @2$4..@-1$4=$3-$2::@>$4=vsum(@2$4..@-1$4)

The result is obviously absolutely not what I'd expect. I don't think that the properties part actually does anything. The result is the same with or without it. Putting it here only to show what I've tried.

emacs org-mode
Edit
Report