writes:

But not every +X floor adjoins a designated X ceiling below. For
instance, consider the +05, +08, +11, and +12 Class B segments around
EWR on the NY TAC (see skyvector.com). What's the point of the + for
those segment floors? A +11 lets you fly at 1100', as opposed to 1099'
without the +. But letting you fly one foot higher is of no value,
since that's much less than the accuracy with which you can control or
even measure your altitude. So why do they bother having the + there?

I'm not sure, but I note that there's a tremendous amount of helicopter
traffic in those areas, and many high obstacles. The Class B also intersects
a number of Class D areas, which may be a factor.