IBU/recipe question

I'm brewing Janet's Brown Ale from Jamil's book. His recipe says 63 IBU. When I throw it into Beersmith, it gives me 76.8 IBU (using the rager formula, which is what jamil's book uses.) and when I scale it to 5 gal batch, 6 gal boil, it gives me 76.6. is this OK?

Janet's Brown Ale
American Brown Ale


Type: Extract
Date: 31/05/2010
Batch Size: 5.00 gal
Boil Size: 6.00 gal
Boil Time: 60 min Equipment: Brew Pot (6+gal) and Igloo/Gott Cooler (5 Gal)
Taste Rating(out of 50): 35.0 Brewhouse Efficiency: -
Taste Notes:

Ingredients

Amount Item Type % or IBU
2.64 kg Light Dry Extract (8.0 SRM) Dry Extract 63.81 %
0.38 kg Wheat Liquid Extract (8.0 SRM) Extract 9.06 %
0.47 kg Cara-Pils/Dextrine (2.0 SRM) Grain 11.28 %
0.47 kg Caramel/Crystal Malt - 40L (40.0 SRM) Grain 11.28 %
0.19 kg Chocolate Malt (350.0 SRM) Grain 4.57 %
1.65 oz Northern Brewer [8.50 %] (60 min) Hops 62.2 IBU
2.00 oz Centennial [10.00 %] (Dry Hop 7 days) Hops -
0.83 oz Northern Brewer [8.50 %] (15 min) Hops 8.3 IBU
1.24 oz Cascade [5.50 %] (10 min) Hops 6.1 IBU
1.25 oz Cascade [5.50 %] (0 min) Hops -
1 items Whirlfloc Tablet (Boil 15.0 min) Misc
1 Pkgs SafBrew Ale (DCL Yeast #S-33) Yeast-Ale



Beer Profile

Est Original Gravity: 1.059 SG
Measured Original Gravity: 1.010 SG
Est Final Gravity: 1.015 SG Measured Final Gravity: 1.005 SG
Estimated Alcohol by Vol: 5.73 % Actual Alcohol by Vol: 0.65 %
Bitterness: 76.6 IBU Calories: 43 cal/pint
Est Color: 21.4 SRM Color:

I think those recipes are scaled for 6 gallons post-boil, 5 gallons of finished beer.
http://www.thebrewingnetwork.com/forum/viewtopic.php?f=7&t=16377

yeah, but since I ferment in a 5 gal carboy, I've been scaling them from a 7 gal boil to a 6 gal, and have been getting the gravities to hit pretty much right on, give or take a couple of points. I was just wondering if the IBU were too outta whack. or should I reduce the bittering addition even more?

once you get above 60 you probably won't even notice the extra 10 ibus. it'll go from very bitter to really very bitter. if you wanna bring it back down to very bitter, then just scale down =D. One of my favorite parts of brewing is altering other peoples recipes to suit my system and taste.