One of the reasons your OG is higher or lower than the recipe creator predicted is, because you mash Efficiency in the recipe creator is not the same as your observed mash efficiency.
Typically we see efficiencies between 70-85% on the grainfather products. But this is subject to many variables such as water pH, grain crush, amount and type of speciality grains used and percentage extraction of your sparge.
Take gravity measurements throughout the brew day. If you know the PPG of your malts (the points per gallon you could extract in laboratory conditions), your original gravity (before pitching yeast) and your volume into your fermenter, you can calculate your Brewhouse Efficiency and adjust for the next time you brew this recipe.
Alternatively, you can make small adjustments up or down each time you brew until you have a Brewhouse efficiency percentage that seems to accurately reflect your process.