I have Libby Pumpkin in my beersmith, in adjunct "add" option, but I think it may have come from some additional file that I added with all sort of canned fruit.
The beersmith profile claims 1.005 SG points per 1 lb of pumpkin. (I have seen some people calculate as much as 1.008 SG points per 1 lb but it's still the same ballpark).
So if you are adding 1.8 lbs to 5 Gallon batch, you will raise SG by maybe .001-.002 (1 or 2 points). Mine went from 1.063 to 1.064 when I add the pumpkin. Bottom line - it will not be super-significant, unless you are one of those people who care about hitting their SG to within 0.1%
Most of pumpkin additions are for flavor/mouthfeel and contains very few fermentable sugars anyways.
See this thread for more details:
https://www.homebrewtalk.com/showthread.php?t=199558