not exactly otherwise that would be horrendously erroneous because the speckle could be a dust or something.
to be more specific - they used computers to analyze light spectrum signature emitted by stars. It's up to scientists to decide on limit of level of spectrum signature to be counted as stars. it's complex.
problem is.... we don't know if those stars still exist or not. It's a difficult to grasp but understandable. 1 Light Year = 5,878,625,373,184 miles. Earth is 93 million miles from Sun. Speed of Light is 671 million mph. So it takes sunlight about 8 minutes to reach Earth.
So since it took 8 minutes for sunlight to reach Earth... imagine how long it took for light from a galaxy far far away to get to Earth. It's most likely over a year so we don't know if the star is still there or not. The stars you see at tonight on your grass is most likely from a few years ago. Hence... a famous opening text.... ""A long time ago in a galaxy far, far away...."
So the only way to find out if the stars are still there or not is to compare the graph from say.... 2000 and 2010 (whenever). Just look and see which one is still there or not. But a huge problem is... a technological difference between 2000 and 2010. Obviously 2010 technology is much more improved and sensitive and 2000 technology is not so it's not an exact science. All we can say is.... "we estimated...."
How I know this? I used to be a space nerd back then and I'm still a trekkie