table formula for the second last row

[Luca Ferrari]

Hi all,
I've a table that is keep growing, and in the end I've added the
following to formulas:

#+TBLFM: @>$3=vsum(@3..@-1)
#+TBLFM: @>$3=round( vsum(@3..@-2)/60 )

but both overwrite the last row of the third column, while I would
like the former to be on the second last row.
Apparently I'm not able to understand how to do @> - 1, and I don't
want to place a fixed row number since the table will add new rows
over the time.
Any help is appreciated.

Thanks,
Luca