I don't think so - the indices taken alone can be arbitrary (i.e. he could have written a,b,c or x,y,z for the indices of V). However when we are taking sums we need to ensure that the indices match.

In other words, I can say that V_{x,y,z }represent the value of the input unit in channel x, row y, and column z, and that K_{e,f,g,h }represents the connection between a unit in channel e of the output and a unit in channel f of the input, with an oﬀset of g rows and h columns between the output unit and the input unit.

Now if want to find Z, all i need to do in the sum (given by equation 9.7) is to ensure that the indices of V and K match up, i.e. using the same subscript (with some slight modification with constants) for **rows in V and the offset of rows in K**, for **columns in V and the offset of columns in K**, and for the **channel in V and the input channel in K**.

Hope this helps!