The person who told me about this was the person who counted up the code at the end of the project. And, yes, it was 250 from each, not 500 from each parent company. (Memory is funny that way.)
I do not doubt that the numbers were rounded for simplicity. It is meaningless to talk about a 499x engineer.
As was explained to me, this engineer assigned two-week work units. If the work was not ready at the end of two weeks, he wrote it himself over the weekend. So, a fair bit of code was written that did not make it into the final product.