This is quite an obscure bit of trivia.

-4.001 at 2 decimal place = -3.99

-1.001 at 2 decimal place = -0.99

-0.001 at 2 decimal place = ?

The answer is 0.00, since the difference between 399 and 400 is 1, same for 99 and 100. The difference between 001 is 000 is also 1.

It is difficult for someone to digest the fact that a number is reduced to nothing.