Sum Index formula - glitch

I'm using the following formula to sum from a cell to the end of the columns.
For instance sum from cell C3 to the end of row 3.

SUM((C3:INDEX(3:3,MATCH(16384,3:3))))

It works except that if I have a dash "-" as the first entry, it seems to go backwards a cell.
In the table below, the yellow cells are incorrect, the sum should be zero.

The dash "-" is required instead of 0.


Capture.PNG

Another option
=SUM(B3:INDEX(3:3,MATCH(16384,3:3)+1))

For the case if you use xls format or old excel version

=SUM(C3:INDEX(3:3;COLUMNS(3:3)))

for new format

=SUM(C3:INDEX(3:3;16384))

SUM function work with used range automatically and range for whole row or column doesn't reflect to calculation time.

Why not just:
=SUM(B3:$XFD3)

Is this too inefficient?

@Gregb11 try to save it to xls format.
however
another one option

=SUM(3:3)-SUM($A3:B3)

@BMV - Why do you care about xls file? the OP attached an xlsx file.

@Gregb11 i think about not only this OP but about anybody who looking for solution.

Thanks to all for the suggestions.
The solutions by AliGW and Fluff13 worked.

Glad to help & thanks for the feedback.