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It would depend on the recipe that you're adding it to. If the specific gravity of the brew without the maple sugar is equal to the specific gravity potential of the maple syrup, then there would be little to no change. If the specific gravity is extremely high and you're expecting a high ABV (12% range), it might actually lower the ABV. Whereas, if you're adding it to a low ABV beer, it may actually raise the ABV slightly.
That being said, if you want the flavor contribution, without a change in your ABV, you'll need to figure out what the potential sugars in that particular brand of maple syrup is, and then dilute it in warm boiled water to the same starting gravity of your recipe and then add it to the beer (either in the boil or secondary).
It's not an easy question to answer, because the recipe that your adding it to has so many variables that need to be taken into account.
Sugars like this are 100% yield if added to the fermenter. It's a simple calculation of dividing the total sugar content by the wort volume after the sugar is added. All you need to know is the potential of the sugar.
You'll need to know the gravity of the syrup. In this case, Maple syrup has a guideline of 66 to 70 brix. You'll add 32 ounces to make 640 ounces (5 gallons) of wort. I'll use the lower guideline number.
Total sugar = 66 x 32 = 2112 points.
Wort Contribution = 2112 / 640 = 3.3 brix = gravity contribution of 1.013.
As long as the units are the same, this scales to any related unit. I could've converted the syrup ounces to gallons (0.25) and divided by 5 to get the same number.
If the added syrup increases the volume, then you'd just add the syrup volume to the batch size and divide with that sum.