With no examples of the data, itself, I can't be certain, but it sounds like the content of cell B2 simply comes first alphabetically - even though it may not look like that's the case. What happens if you sort the same range in Z-A order rather than A-Z - does the content from B2 go to the bottom of the list?
However, when you do as you're doing, Expand the selection applies vertically as well as horizontally, so rows 28 & 29 are being included even though you indicated that don't want them to be. If you want to exclude rows 1, 28 & 29 I'd suggest that you select A2:N27, tab as necessary to have a cell in column B as the active cell in the range, then sort in alpha order.
Another option would be to insert some rows between 27 & 28, sort the primary range, then delete the extra blank rows.