0:0:0:0:0:0:0+1-1

Most straightforward interpretation: treat the colons as separators for zeros being added.

Compute: (0+0+0+0+0+0+0) + 1 - 1 = 0 + 1 - 1 = 0.

So the result is 0.

If you meant a different meaning for the colons, tell me and I’ll re-evaluate.