I'll give an example to understand what's going on here.
I have 5 NSG's at one area and an another NSG nearby to that place, but not exactly at the same place. If I place the cursor on that single NSG, a little window pops up which gives the location of the NSG, after this the NSG icon disappears and joins the other 5 NSG's, now the count will be 6 and the window will not go away.
Attached the screenshots of it before and after.
Before -

After -
