Bon don’t worry about those yellow balls — they are usually called plugs and as Sue said above that’s a GOOD sign you are clearing them, and means your airway clearance is working.
It’s good to keep tract of the amount of mucus and plugs, so you know if there is a big change (good or bad) happening in your lungs.
I’ve done airway clearance now for four years, and ususally clear 1/8 cup mucus and about 9-10 of those small yellow plugs.