[lojban-beginners] ba bo and pu bo

["Anand Deopurkar" <anand.deopurkar@gmail.com>]

Why do ba bo and pu bo mean opposites of what they should mean?

For example, la meris klama ba lenu mi klama fi le kumfa. (Mary came after I left the room)
should be equivalent to - la meris klama .i babo mi klama le kumfa. 
However (http://www.tlg.uci.edu/~opoudjis/lojbanbrochure/lessons/less10connect.html) says that
ba bo means "after wards." It also hints that this is because of its similarity with baku, but it still bothers me.

-Anand