Description of kernel.printk values

Between Debian 5 and 6, the default suggested value for kernel.printk in /etc/sysctl.conf was changed from kernel.printk = 4 4 1 7 to kernel.printk = 3 4 1 3. I understand that the first value corresponds to what is going to the console. What are the next 3 values for? Do the numerical values have the same meaning as the syslog log levels? Or do they have different definitions? Am I missing some documentation in my searching, or is the only location to figure this out the kernel source.