Why group ala/epa/dha as omega-3 since ala has very limited % can be converted to dha ? very confuse.

Buy what you need: The key to avoiding all this confusion is to buy what you want or what you need. That means a person should not buy the "precursor" compound or supplement, and then try to figure out how much of it is converted to the active compound that he really is interested in. If one buys only the active compound, he has no confusion at all.