How to reduce grain bill to compensate for higher efficiency?

[TkmLinus]

I BIAB and since I starting milling my grains really fine my efficiency has gone way up. Most brews(from pre-packaged kits) are coming out 1-1.5% higher ABV than intended(first world problem, I know..) With a certain grain bill, if I want to reduce the ABV from 7% to 6% can I simply reduce the weight of all grains by 1/7 to reduce the ABV by about 1% or am I over-simplifying things? Thanks in advance!

 

[VikeMan]

There are software-aided ways to work this out more precisely, but your method would be fine for a first approximation.