Everything is relative; based on your test you can determine there was a reduction in po4. I personally don't believe a phosphate test can be accurate in most situations, just because if you have algae, you will still get a low reading. My tank was reading 0.03 on a Hanna, which is where most people would say is ideal, but you could clearly look at it and determine there was more in there, or there would not have been GHA all over the place. Finally getting that back under control though.