I have to say the whole "First Grader" "Fourth Grader" magazine stories kind of frustrate me from an archival perspective. They are sometimes infuriatingly difficult to quantify, and not just in Astro Boy, but the stories from Jungle Emperor, Unico and many others.
So are you saying that the story in both Fourth and First Graders were the same (i.e. Astro Boy Returns)? I know they sometimes had a habit of crossing "boundaries" as the readership grew. So a story that started in First Grader might end up in Fourth Grader if the serialization went on long enough (even though most are self-contained stories). I've also seen self-contained stories spread out among several of them that are later collected together (mainly for the "Leo-chan" version of Jungle Emperor), but this would be the first time I've seen the same story serialized in two magazines at the same time, albeit on a different release schedule.
I'm going to re-check the Astro Boy vol. 22 bit when I get home to check. I've been doing a chronological re-read but I'm only as far as the "Count Bat" story from... 1959?
![Wink ;)](./images/smilies/icon_wink.gif)