IBUs from Beersmith vs Kit Label

I am brewing a Brewer's Best India Black Ale kit for my fourth homebrew. I just installed Beersmith on my computer so I could switch from kits to designing my own recipes and thought I'd give it a test run by inputting the kit recipe. The kit advertises 80-85 IBUs but Beersmith is telling me it will only be 35.8 IBUs which is clearly a pretty drastic difference. I'm mostly wondering where the discrepancy is coming from so I'll be able to account for it in the future and am confident the kit will probably taste fine.

Further info:
The weights, boil times, and AA% are correct on BS and are as follows
.75 oz 17.4% for 60 min
1 oz 10.9% for 40 min
1 oz 10.9% for 5 min
2 oz 10.9% dry hopped

TIA for any help. Even though this is my first post I've already learned plenty from this forum.

Are your volumes correct - e.g. 5 gallon batch?

Yep, I should've mentioned that. 5 gallon batch and all other estimates (OG, abv) come out correctly.

One extenuating factor I just considered is the kit uses special dark extract (90 deg) which I just plugged in as dark which is listed as 17.5 SRM, but I'm assuming it's not all roast bitterness?

I entered your hop schedule into my BeerSmith and got 86.1 IBUs.

You have some variable in BeerSmith configured incorrectly. Go through and double check everything. Since you're new to BeerSmith, you'll need to set up a custom equipment profile with the average boil off rate/loss to trub, etc. for your personal equipment as well. The numbers are always dead on if you configure everything properly.

Factors? you have to change the AA % to match your hops package, the generic values in BS are wrong.
Also Brewers Best kits have 2,5 gallon boils, that has an effect on hops utilization as well.

TopherM said:

I entered your hop schedule into my BeerSmith and got 86.1 IBUs.

You have some variable in BeerSmith configured incorrectly. Go through and double check everything. Since you're new to BeerSmith, you'll need to set up a custom equipment profile with the average boil off rate/loss to trub, etc. for your personal equipment as well. The numbers are always dead on if you configure everything properly.

Click to expand...

I figured it out. I changed the default 3 gallon boil pot to 5 gallons. Could someone wiser than myself explain why this is? I use a 5 gallon kettle but only boil 3 gallons. Does this lower my hop utilization?

Edit: Looking at it more closely, it pretty drastically changes the yields on everything. It looks like the change is from the extract to mini-BIAB switch. I should probably read more on the BS site, haha.

Thanks for the help everyone.