Graham Wheelers beer engine

[twentyfootwilf]

When using Graham Wheeler's beer engine to work out brews using kits as the base would it be correct to call the kit eg a coopers dark ale, 1700 grams of dark liquid malt extract or would the use of any speciality grains within the kit make the fermentability of the kit less predictable than a straight forward tin of dark malt extract. Hope that question makes sense!