-bottom properties refer to *-right properties in the layout rules.

"
6. 'right' is 'auto', 'left' and 'width' are not 'auto', then solve for 'right'
"

'top' + 'margin-top' + 'border-top-width' + 'padding-top' + 'height' + 'padding-bottom' + 'border-bottom-width' + 'margin-bottom' + 'bottom' = height of containing block

So:

     80px : top
  +
      0px : margin-top
  +
      0px : border-top-width
  +
      0px : padding-top
  +
     80px : height
  +
      0px : padding-bottom
  +
      0px : border-b