I feel like I'm missing something very obvious, but I can't figure out what.

Suppose I'm SM0, shooting at a SM0 target at 20 yards (-6) so a total of -6 for these factors

- If the target is 10 times farther away, it's another -6 for total -12
- If the target instead is 10 times smaller, it's -6 for total -12
- If instead
*I'm* 10 times smaller, shouldn't it be -6 for that, and total -12? (I couldn't find it in the rules, but it would seem sensible, to me.)
- If those are all correct, then if I shoot at something that's the same SM at a range that's fixed multiple of my size would be increasingly difficult with increasing size. Say SM0 -> SM0 at 20 yards = -6, or SM6 -> SM6 at 200 yards = -12.

What am I missing? Shouldn't the attacker's SM matter for ranged combat?