Kit IBU vs. Beersmith IBU

First, thanks to everyone who contributes to this addictive site... so much great information!

My very first all-grain BIAB is going to be a morebeer IPA kit. The instructions that came with it say it clocks in at 55-60 IBU, but when I enter the recipe in Beersmith I'm hitting up to 100 IBU. I like it hoppy, and I'm sure it'll be great beer, I'm just wondering why there's such a big difference for future reference when I start dialing in my system and making my own recipes. Also, is there any way to adjust the mash eff. in Beersmith -- 86% seems a little ambitious my first time out... Any advice would be appreciated. Thanks!

Boil Size: 6.74 gal
Post Boil Volume: 6.24 gal
Batch Size (fermenter): 5.00 gal
Bottling Volume: 5.00 gal
Estimated OG: 1.070 SG
Estimated Color: 5.2 SRM
Estimated IBU: 100.6 IBUs
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 86.4 %
Boil Time: 60 Minutes


Ingredients:
------------
Amt Name %/IBU
11 lbs Pale Malt (6 Row) US (2.0 SRM) 80.0 %
2 lbs Pilsner (2 Row) Bel (2.0 SRM) 14.5 %
12.0 oz Caramel/Crystal Malt - 15L (15.0 SRM) 5.5 %
1.50 oz Magnum [14.20 %] - Boil 60.0 min 60.4 IBUs
1.00 oz Columbus (Tomahawk) [16.30 %] - Boil 30. 35.5 IBUs
1.00 oz Centennial [8.50 %] - Boil 1.0 min 1.0 IBUs
1.00 oz Citra [13.50 %] - Boil 1.0 min 1.7 IBUs
1.00 oz Columbus (Tomahawk) [16.30 %] - Boil 1.0 2.0 IBUs
1.0 pkg Dry English Ale (White Labs #WLP007)
3.00 oz Falconer's Flight [11.40 %] - Dry Hop 5. 0.0 IBUs

Not that it matters a ton probably but check the Alpha Acid percentages on your hops. It's possible you have a lesser percentage hop. By the way I get 80 IBU's from that magnum too.

You probably are ok at a brew house efficiency of 72%. That's pretty reasonable and that is the number most people look at rather than mash efficiency.

Okay, good to know 72% brewhouse eff is reasonable...
Yeah, i plugged in all the AA% for all the hops and still came out 40 IBU's high...
Thanks for the help

One big problem is with the recipe itself. It has no hop flavor additions. Just a big 60 min addition with the magnum...then a fairly large IBU, but in-efficient Columbus bittering addition at 30 mins...then aroma hops basically at flameout.

Reduce the Magnums to 1 oz at 60, move the Columbus from 30 mins to 20 for flavor (and reduces the IBUs.) This should get you back in the right IBU range (60-70 total). Double check all your BS2 settings also. The kit IBUs have to be wrong with 1.5 oz magnums at 60 then those 16.3 % AA Columbus at 30.

So busy with the process of my first AG that the lack of flavor additions hadn't even occurred to me. Brewed it yesterday and it's bubbling away this morning!