Extracts, from what I've read here on the forum, aren't as fermentable.
That, of course, depends on the extract. Some, such as Breiss Pils extract, I have found to be highly fermentable. It's all I use for the last several years. That said, I agree that it would not be unlikely that an extract nut brown ale would have a high finishing gravity.
By the way, most homebrewers here (including me) will tell you to skip secondary next time and just let the beer sit in primary for 2-3 weeks - then bottle. Reasoning -- Transferring introduces oxygen which is a worse risk than leaving it on the yeast (this is really a problem for commercial breweries and large fermenters). Also, removing the beer from the yeast prevents the yeast from cleaning up those green and off flavors.
I would also add that secondary is just plain not necessary and you can skip the effort. I'm kinda lazy and short on time, so anything to gain a little efficiency in the process is a bonus.
Please post your recipe/process so we can further evaluate.
Yes, and it would be helpful to know what extract was used as that might give a clue as to it's fermentability.