Hi all the attached picture(sorry for orientation) is from Andrew Smith, s book "Building The Victoria"

I am a bit confused by the highlighted text.
How can it be dead center and at the end of its stroke.
Am I missing something or is it a typo.
Edited By Arthur Goodwin on 25/02/2021 22:48:58
Edited By JasonB on 26/02/2021 07:05:59
Edited By JasonB on 26/02/2021 07:06:40