It means that you have trapped air inside your loop. It could be hidden in the radiator for example. You should try to tilt the system to different positions while the pump is running. This way you can help the air to move into the reservoir.
Hmmm. I've had the system running for 7-10 days, have done lots of tilting with the case in all 4 directions to get air bubbles out. I can't seem to find any other air bubbles.
I've also run the Leakshield deaerationion about 5 times in total now. The fill level never changes after the process is complete (indicating no removal of air).
Also, the fill level may be incorrect although not terribly so. It's reporting 63% reservoir filled. From the visible glass area of the reservoir which I measured to be about 185 mm (not below/above the visible glass where the black plastic is), the water reaches about 130 mm. 130 of 185 is about 70%. Could this number possibly being off have an affect on other tests and results?
I'm assuming the fill level % is one of many sets of stats that the AquaSuite and Leakshield "brains" use for their functions...