Writing direction RTL and width

If the writing direction is right-to-left, it appears that the a cue can go
out of bounds.

"If the text track cue writing direction is horizontal, the text track cue
alignment is end, and direction is 'rtl'
Let maximum size be the text track cue text position subtracted from 100."
http://dev.w3.org/html5/webvtt/#cues-with-video

"If the text track cue writing direction is horizontal, the text track cue
alignment is end, and direction is 'rtl'
Let x-position be the text track cue text position subtracted from 100."
http://dev.w3.org/html5/webvtt/#cues-with-video

For example, at position 44%, width should become 56%, and left 56%.
For a video with width of 100px, this would result in a box from 56px to
112px.

Now if the width is expanding left instead of right this would make sense
(0px to 56px) but I cannot find anything that states RTL width expands
left. It appears that width is always to the right of the left position.

Thank you,
Kyle Barnhart