Objects that "exist" but cannot be seen or selected?

[David J. Potter]

I am editing some existing plans for a client of mine taking groups of objects from one layer and transferring them to newer, named layers.
The reason for is, over the versions-years older plan layer names have antiquated in terms of organization and newer abilities of Chief which makes perfect sense.

What does not make "perfect sense" is that after transferring all visible objects to the new layer by marquee-select and or using the : layer-painter/eye dropper while in the "All Off" layer set (only the layered objects that I want to move to the newer layer names/sets/anno sets is turned "on" for easy handling) there still shows a "red plus sign" in the "Used" column even after marquee-select one floor at a time and in camera views, nothing is "there", yet the software insists there is something "there".

This is not ruining my Life but if there is an answer to this conundrum, I would like to hear a possible-reasonable explanation.

I have seen this occur over the years from time to time and just skipped it because it is no big deal in terms of getting my work done but I would like to understand how this might be caused to occur please, if anyone actually knows.

DJP