Ah, gotcha!
I guess the "easy" way to think of it is that all grains that go into a mash need to be converted, no matter what they are. If you are using mostly malted grains, there is almost always more then enough diastatic power to convert so you don't really have to think about it. If you don't have conversion, you just get a ton of starch but generally conversion in a proper mash happens in as little as 20 minutes so it's not something to worry about.
The only time this could be an issue is if you are using a ton of rice or unmalted oats or corn (40% or more) or other weird unmalted grains and then you'd have to consider the DP of the base malt to convert that. For most usual brews or recipes, it wouldn't be an issue at all. So if you're using something like flaked oats, just using an equal amount of base malt would "cover" you for conversion. My tip there is for extract brewers/partial mash brewers- If you're using flaked grains, use an equal amount of base malt in your steep/mash, and then you'd be all set.