No need to worry. Here is the explanation from the EAC manual:
A Track quality of 100% obviously means that the track was extracted 100% correct. But here's where some people make mistakes; sometimes EAC rereads certain audio sectors multiple times to get accurate extraction results. For every reread EAC does, the Track quality decreases, but this does not mean that the extraction is less accurate. It is possible to have a bit-by-bit perfect copy of a track, while Track quality is lower than 100%. As long as Exact Audio Copy does not report any errors in the Status and Error Messages log, the extracted files are bit-by-bit perfect copies of the original. Track quality should be interpreted as the physical quality of the CD and not of the extracted data. A CD with some scratches or dirty fingers on will certainly cause rereads in EAC and thus a Track quality lower than 100%, but still the extracted tracks may be perfect. Thus if the log says Copy OK for a track that means it's extracted perfect - no matter of the Track quality.
This was copied from http://users.pandora.be/satcp/eac07.htm#-