1) It seems that one video is missing in this section :
Unit 3.1.D.1 Require Learners to Make Relevant Distinctions
“How can we make 28 with blocks ?”
[Video 3.1D1; transformation]
2) In the last example with fractions “What choices do learners have to make ?”, a given is implicit : what is one unit here ?
A rectangle with one “1” in it and the mention “Here the area of this rectangle represents one” would be necessary here to me.