The tutorial DOES tell you exactly how to remove leaks and even explains why it leaks. What else do you want?
Basically any trigger you have in your map that that creates a unit at a region leaks. To fix this, you have to create a point variable, then in the trigger where you spawn units, set that point variable to a point in whichever region you want your units to spawn. Then Create your units at your POINT Variable, then destroy the same Point Variable with custom script at the end of the trigger. It's not rocket science.