1024 is too close to 1000 for it to actually matter - the ND filters have much larger variation than that. A 10 stop filter is more likely a half or maybe a full stop darker or lighter than the nominal 10 stops.
Agreed.. I was just being precise about what a 10 stopper is doing. Just use 1000 times your shutter speed without the filter and you'll be fine. The difference between 1000 and 1024 is not worth worrying about.