When making formulas using table automation, Excel puts the @ symbols in automatically. Sometimes, they aren't necessary and if you take them out, the formula returns the same result. Other times, not so much.

It seems to me is what it's saying is: take the cell in this row (i.e. the same one as the formula is in) @ this column and do some operation with another cell @ this column.

e.g. =([@Widgets]-[@Flanges])/[@Flayrods]

If Widgets are in A, Flanges in B, Flayrods in C, that is how the equation would appear if you enter the formula in D2 and clicked the cells in A2, B2, and C2 to generate it.

I can take out the @ symbols and the equation works fine.

=([Widgets]-[Flanges])/[Flayrods]

However, if I do a sum of the same columns, the equation appears as:

=SUM(Parts[@[Widgets]:[Flayrods]])

Take out the @ symbol, and the formula returns a #REF! error.