What Houzzers are commenting on:
“You have one main color, which is usually your neutral, and this is applied to 60 percent of the space. Then you do another 20 percent in a contrasting or complementary color, and then break it down to make up the different proportions, roughly 10 percent each in accents.”
Proportion is the scale of objects and how they compare to each other. Proportion is used well in this photo. The tables and chairs feel appropriately sized, and compare well to the bookshelf. All of these items fit well into the room and still give space for an open feel that is appropriate for a dining room.