Interesting class B airspace

I ran across an interesting notation for the floor of a class B airspace. It is common to see notation that use "-" to indicate that a class D airspace goes up to but does not include an altitude. An example of this is KSQL class D airspace on the east side of the airport. It has a designation of [-15] which indicates that the Delta airspace goes up from the surface up to but not including 1500 MSL. It is also common to see "T" used for the ceiling of class C airport to indicate that the ceiling extends to the top of the overlying airspace. This is used in the KOAK class C airspace.

In the New York area, I ran across a unique notation that I hadn't seen before. One of the shelves of the class B had a notation of "+" for floor of the airspace. In the chart to the right, you can see the +05. This indicates that the floor of this airspace starts "above" 500 MSL but does not include 500 MSL.