And how does cfstats track the maximum size? What does "Compacted" mean in "Compacted row maximum size".
That maximum size is "the largest row that I have encountered in the course of compaction, since I started."
Hence "compacted," to try to indicate that it is not necessarily the row of maximum size which currently exists. For example, if you had a huge row at some time in the past and have now removed it (and have not restarted in the interim) this value will be misleading.