Another way they could have written would have been as "10 millionths of a billionth of a billionth of a second", which is still damn awkward but at least reads correctly and I assume is what they meant.
I think they meant 10 million billionths of a second. But personally I like "tiny fraction of a second". I find it hard to believe that amount of time could be measured, so it's likely a calculation or a theory anyway.