Overflow box with width as length

Overflow box 'width' 400px

1a.
1b.
1c.

Containing block width =

Scrollable box 'width' 825px = ('margin-left' 25px + 'width' (400px x 200%)800px + 'margin-right' 25px~0px).

Overflow box 'width' 400px

2a.
2b.
2c.

Scrollable box 'width' 875px = ('margin-left' 25px + border-left-width 25px + 'width' (400px x 200%)800px + 'border-right-width' 25px + 'margin-right' 25px~0px).

Overflow box 'padding-left' + 'width' + 'padding-right' 500px

3a.
3b.
3c.

Gecko 1.8: Scrollable box 'width' 975px = 'padding-left' 50px + ('margin-left' 25px + border-left-width 25px + 'width' (400px x 200%)800px + 'border-right-width' 25px + 'margin-right' 25px~0px) + padding-right' 50px.

Gecko 1.9 & Safari 3: Scrollable box 'width' 925px = 'padding-left' 50px + ('margin-left' 25px + border-left-width 25px + 'width' (400px x 200%)800px + 'border-right-width' 25px + 'margin-right' 25px~0px) + padding-right' 50px~0px.

Opera 9.5: Scrollable box 'width' 1025px = 'padding-left' 50px + ('margin-left' 25px + border-left-width 25px + 'width' (400px x 200%)800px + 'border-right-width' 25px + 'margin-right' 25p) + padding-right' 50px + mystery 25px.

Overflow box 'border-left-width' + 'padding-left' + 'width' + 'padding-right' 525px

4a.
4b.
4c.

Opera 9.5: Scrollable box 'width' 1050px = 'padding-left' 50px + ('margin-left' 25px + border-left-width 25px + 'width' (400px x 200%)800px + 'border-right-width' 25px + 'margin-right' 25p) + padding-right' 50px + mystery 50px.

the extra 25px in Opera 9.5 is due to the 'border-left' of the overflow box. This does not happen with 'border-right'