[css3-animation] keyframes and percentages

Hi,
The spec is a bit silent about that, but is it ok to have negative 
percentages or percentages over 100%?
It is not specified at all, so it should be allowed, and if you have
-20% {
   top: 10px;
   animation-timing-function: ease-out;
}
20% {
   top: 20px;
}
The animation should still start at 0%, so from a point in the curve 
defined by the ease-out function.
Was that the intent? (and so should it be explicit in the specification?)
Cheers,

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves