Airbus writes:

Trying to read between the lines of this incredibly weird post, it would appear
the writer is suffering from the illusion that "fractional" airspace altitudes
in a given segment are indicated both for the charted (Class B) airspace and
for the underlying (Class E). Readers should be advised of the fact that this
expert, offering his "presumptions" may never have seen a sectional chart, and
certainly has never studied the subject - does not know how to read the chart.

Okay ... so explain why the charts include + and - for altitude limits on
airspaces?

I already know the answer, since I looked it up ages ago, and I've given it,
but I'll try again:

If you see, say, 50/SFC for a Class C, and 80/50+ for a Class B above it, it
means that the Class C extends from the surface to 5000 feet inclusive, and
the Class B extends from 5001 feet to 8000 feet inclusive.

Without a plus or minus sign, there is an ambiguous margin of 100 feet between
the airspaces. For example 50/SFC for the Class C and 80/51 for the Class B
means that the area between 5001 feet and 5099 feet inclusive is in neither
airspace. Since this could cause problems if someone were to actually try to
fly through this thin slice of air, calling it uncontrolled, the + and - are
used to make it clear that the two airspaces touch each other, with no space
between.