Well, I checked on ancestry images of the census and my best guess is that last column is the number in agriculture. The reason I think that is because 1. Joseph has only 3 males in that household and 2 are 10 or younger and 2. the census taker started making the census enumeration shorter around page 190 (sheet 28 of 98 on ancestry) and what he did was cut out all the columns for slaves and free blacks and left the columns for ag., commerce, and manufacturing. I went through the pages and noticed that almost all of them had at least 1 person in ag. and so it the end I am betting that is the only column the census taker felt worthy to continue recording.