This div has a width set to 360px, with 7px of padding all round and 6px margins. The div has a grey background to show the padding, and a 2px thick blue border.
The div is itself is within a container div- this has width=390px (360 width +7+7 padding +6+6 margins +2+2 borders). The container has margins and padding set to zero, and a white background.
The paragraphs have margins set to 0, font-size set to the browser default, white background and green borders.