Fifteen circles are rendered in a horizontal row across the browser viewport, each with a radius of 20 pixels. The example demonstrates how to bind an array of numbers to SVG elements using D3’s `data()` and `enter()` selection methods. The code uses `d3.select` and `d3.range` to generate the data and append circles to an SVG, with x-positions calculated as `d * 50 + 50` and a fixed y-coordinate of 250. Rendering is done via inline SVG in the HTML document.