That probably means that one-third of 9/26 polling (a single day’s worth of polling) was post debate and 2/3 was pre-debate. Just a guess. If so, then the post debate portion of a 7-day rolling poll would be 1/21 or 0.048 percent.
Oops, my bad: 0.048 percent should have been 4.76 percent. So, if 1/3 of a day’s polling bumped it up for Trump that is big.