Question is about a paper “A Block-sorting Lossless Data Compression Algorithm” by M. Burrows and D.J. Wheeler

Question

In the paper A Block-sorting Lossless Data Compression Algorithm by M. Burrows and D.J. Wheeler Link. On page number 5. please describe this line

If the original string $S$ is of the form $Z^p$ for some substring $Z$ and some $p > 1$, then the sequence $T^i[I]$ for $i = 0,...., N - 1$ will also be of the form $Z'^p$ for some subsequence $Z'$.