I'm curious about the theoretical background of choosing m corresponding to the number of chains and t corresponding to the chain length in the rainbow table.

[sysbm04]

Hello
I'm Kim Doo-soo from Korea University in south Korea.
I'm curious about the theoretical background of choosing m corresponding to the number of chains and t corresponding to the chain length in the rainbow table.
For example, I wonder why m=67108864 and t=803000 are 9 digits of the password in this source code.
Please reply. Thank you.