A good question, but the answer is fairly easy. NHC provides NRL with the center coordinates for all Invests. On July 6th at 18Z NHC assigned updated coordinates of 10.9N 55.3W for the old Invest 96L - but it looks like NHC forgot to tell NRL to drop the Invest, so the Navy keeps the Invest active awaiting new coordinates or instructions to drop the Invest. Since that time, a new tropical wave has coincidentally moved into the image frame of the last coordinates for the old 96L - so it looks like a new Invest (and eventually it might be) but for now, its not. Hope that you were able to follow this.
Cheers,
ED