1)
Seeing as they had just broken the Shabbos, how can the Torah write that they kept Shabbos?
1.
Rashbam: The Pasuk means that from now on, they kept the Shabbos.
2.
Because the people at large kept Shabbos. It was only a handful of people who broke it. According to the Midrash, it was Dasan and Aviram.
