新聞 and 雑誌: publication and reading scope
Distinguish publication names, issue dates, and what was actually read.
Reading a newspaper
新聞 (しんぶん) means newspaper. 「新聞でその知らせを読みました」 means reading the news in a newspaper.
「今日の新聞はまだ読んでいません」 says today's newspaper has not yet been read. It does not say it was not published.
Choosing a magazine
雑誌 (ざっし) means magazine. 「旅行の雑誌を買いました」 means buying a travel magazine.
「雑誌の最新号を借りました」 says the latest issue was borrowed. 最新号 identifies one issue, not all past issues.
Medium and overall scope
「雑誌の記事を一つ読みました」 means reading one magazine article. Do not expand that to the entire magazine.
「新聞にも雑誌にも載りました」 says it appeared in both newspapers and magazines. It does not establish publication in every newspaper and magazine.
Does reading one article mean reading the whole magazine?
Show the answer and why
No. The stated reading scope is one article.