The names of the classes are not economic; they're political†. They have to do with one's ability to influence politics.
The "middle class", i.e., the borgeoisie, are the class of business owners (and/or people who have the ability to start a business, i.e. who have a professional skill that could be sold freelance or with a one-person company "wrapped" around it.) What do you call a lowest-income-bracket-for-business-owners business owner, other than "lower middle class"?
Meanwhile, a laborer—even a rich laborer (e.g. a waiter who makes a lot in tips; or a unionized dock-worker; or a soldier)—is, definitionally, in the lower class. If your professional skills are only in demand in the context of a capitalist organizing and value-adding on top of them, then you're in the lower class. (For example: dentist? Middle class. Dental hygienist? Lower class. The dentist can start their own dental clinic, whereas the hygienist cannot. Even if they both took home the same salary from said clinic, one has access to corporate profits—capital—while the other does not.)
People don't say "upper lower class", but the French equivalent "prolétariat riche" does make sense. (There are whole sectors of the economy that cater mostly to the prolétariat riche. Anything referred to as "bling" is marketed mainly to the prolétariat riche. Nightclubs cater mostly to the prolétariat riche.)
† In English, the terms are mapped to positions on a city's height map (lower/middle/upper), because cities used to be basins of smoke and filth, and the people who could, would move to the outlying hills to be away from it. But this is still a political distinction, not an economic one. No matter how wealthy you are, you can't get away from city life entirely until you no longer need to work for a living at all. Once you don't need to work at all, you unlock the time+energy+liquid assets required to influence politics. It's all part-and-parcel.