Comment by mikepavone

This is a small point, but calling the 33-byte unit a sector in CDDA is a bit misleading and probably incorrect for the quantity being labeled. This is a channel data frame and contains 24-bytes of audio data, 1 byte of subcode data (except for the channel data frames that have sync symbols instead) and the rest is error correction. This is the smallest grouping of data in CDDA, but it's not really an individually addressable unit.

98 of these channel data frames make up a timecode frame which represents 1/75th of a second of audio and has 2352 audio data bytes, 96 subcode bytes (2 frames have sync codes instead) with the remainder being sync and error correction. Timecode frames are addressable (via the timecodes embedded in the subcode data) and are the unit referred to in the TOC. This is probably what's being called a sector here. Notably, a CD-ROM sector corresponds 1:1 with a timecode frame.

Note: Red book actually just confusingly calls both of these things frames and does not use the terms "channel data frame" or "timecode frame"