No, ye do not go into negatives. The reason why is that if ye were to do so, 'twould just reverse the mesh. Ye will need to use decimals. This is when all those boring math classes ye took at school kick in. The more decimal places ye 'ave, the smaller the mesh will b'come. I'd recommend trying 0.001 first and see how that works. Ye will just 'ave to mess 'round with the decimal places and see what ye like best.
If ye get confused, do say so, us floofs would be happy to help further. ^3^