That's almost 82% attenuation. That's very reasonable with that yeast, that malt bill, and that mash temperature.
I don't think there are any online calculators that take mash temp, ingredients, and the yeast's probable attenuation into account when they give you a projected FG. You could have mashed at 155, and it would have finished at 1.017. You could have mashed at 147, and it might have finished at 1.008, if the yeast could be pushed to it.
A good rule of thumb is to find out the yeast strain's average attenuation (or the attenuation you usually get with that strain) and add or subtract a few points based on the mash temperature and ingredients.
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