What is the Difference Between "Sustainable Listening" and "Listening Time" for Earbuds?

I'm looking for new discreet earbuds. The listening time is very important. As you can see from the pic, there are 2 different times. Idk which one is the actual time the battery will last while continually playing. 4-5 hours is fine. 1.5 hours is not good at all.