What does the Track Quality really mean? A few times I get 99.7% or 97.5%. But there are no suspicious position reported.

When you get 99.7% and so on, that means that a bad sector was found, but the secure mode has corrected it – from 16 times of grabbing the sector, there were 8 or more identical results. So it only indicates read problems. It is the ratio between the number of minimum reads needed to perform the extraction and the number of reads that were actually performed. 100% will only occur when the CD was extracted without any rereads on errors. ONLY when there are suspicious positions reported, there are really uncorrectable read errors in the resulting audio file.