Further Info Needed

Hi, im going to try out the multi db thing, however im not sure i understand this part.

4) Copy blog tables (and related plugin tables) to the new blog databases. Blogs are assigned to databases based on an md5 hash of the blog id. You then take the first character for 16 databases, 2 for 256, and 3 for 4096.

how would i decide which id goes where?

would blog id 256 go into database 2? if so why would blog id 4096 go into databse 3?