Hi @littlepencil and @asuleo -
InVEST 3.2.0 is VERY old and we no longer support it. I recommend using the latest version, which is 3.9.0. Some of the parameters and outputs of version 3.9.0 are different than the 3.2.0 nutrient model, so if you are actually running InVEST 3.9.0, but looking at the User Guide for 3.2.0, there will be a lot of inconsistencies. Please see the User Guide for 3.9.0 instead.
And as I noted in this post from @asuleo, unfortunately the current NDR model does not provide a nutrient retention result.
~ Stacie