Issue on "Series"?

Hi, I’m trying to study grid-based design by re-making this video https://youtu.be/b8pAQ1OFbZQ?si=2CAkV_Oz--jpzO_I


But when I’m trying to move it vertically (unit z) and adding count + distance, my grid suddenly became kinda stepped/exploded I don’t know how describe it.

May anyone tell me what I’m doing wrong? Thanks in advance.
Grid tower study.gh (8.1 KB)

Graft your series output.