Example Character Sheet: https://www.dndbeyond.com/characters/29069854/ODwFWq

The Genie subclass for Warlocks has a 6th-level feature called "Elemental Gift." It states:

"You begin to take on characteristics of your patron’s kind. You now have resistance to a damage type determined by your patron’s kind: bludgeoning (dao), thunder (djinni), fire (efreeti), or cold (marid).

In addition, as a bonus action, you can give yourself a flying speed of 30 feet that lasts for 10 minutes, during which you can hover. You can use this bonus action a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest."

(Emphasis added)

However, my character (who just leveled up) has a proficiency bonus of +4... yet I'm still only given 3 slots to use the ability on the DDB character sheet.

Now, the character is multiclassed, and just got a bump in proficiency bonus so perhaps the feature is only looking at levels of Warlock to determine what the number of uses should be? Still, it's an error that doesn't match the actual RAW.

The answers you seek are in the thread specifically dedicated to that particular Unearthed Arcana article:

https://www.dndbeyond.com/forums/dungeons-dragons-discussion/unearthed-arcana/67520-ua-may-2020-subclasses-revisited

Ah, thank you for that... didn't realize there was a place specifically for UA bugs.

A little surprised that I determined the background behavior correctly.