The mishnah reflects two issues: what can we talk about and think about on Shabbat, and what can we plan to do after Shabbat? Tchum Shabbat - how far can one go on Shabbat in preparation to hire workers after Shabbat? The Gemara then applies the mishnah, to determine its specific case, including explanations why it can't mean the more general case. Also: when you cannot say something on Shabbat, but you can hint to it. And: Some of the things that appear on this daf as permitted are surprising - apparently, for the sake of Heaven, but still surprising. Plus: Waiting to bring harvest in right after Shabbat, and discovering a hole in the fence... Which he can't fix on Shabbat, so a bush grows to fill in the gap. To some extent, that kind of miracle involves paying attention. Note: And the Gemara asks this question: what about Havdalah? Namely, if you're sitting waiting for Shabbat to end to take care of hiring workers, etc., you need to make Havdalah! Apparently, this point at the edge of tchum Shabbat was near a winepress... Alternatively, say "Hamavdil"!