what is the shape of signal before feature extract module?

[Stride99]

Hello,your work is wonderful and I have a question about it.Since we extract a subsequence of length l = 31 around each relevant CpG position.For each subsequence, we extract corresponding p signal points. Then we reshape it to s*b,where s=p/b.

I just don't understant why the shape is not include l(31)?And how to get p signal,is random sample,or other way?