The implied information is that it was during the entire week of the festival. AT: "from the first day to the last day of the week" (See: [[rc://en/ta/man/translate/figs-explicit]])
"They made a feast" or "They celebrated the festival"
# on the eighth day
"on day 8" (See: [[rc://en/ta/man/translate/translate-ordinal]])
# solemn assembly
This was a special religious gathering.
# in obedience to the decree
The implied information is that "the decree" was the command of Yahweh about how the Festival of Shelters was to end. AT: "as God had commanded" (See: [[rc://en/ta/man/translate/figs-explicit]])