My daughter brought this worksheet home today too.
You have 913,256 as the problem. We know that if we work from 6 over the #'s are in these places: 6 in the ones, 5 in the tens, 2 in the hundreds, 3 in the thousands, 1 in the ten thousands and the 9 in the hundred thousands spot.
They teach the kids to group these. So the one spot, ten spot and hundred spot are called ONES PERIOD. The thousands, ten thousands and hundred thousands are grouped in THOUSANDS PERIOD.