Battery still says it’s degraded after replacement?

I got my battery replaced yesterday. But I still have some concerns about it. First off, I charged my phone around 6 pm when I got home from the Apple store because my phone was at a low percent. Around 9 pm, it was done charging, so I unplugged it. I went to sleep, and the next morning, it was at 61%. Why is that? Also, my battery still says it’s degraded. I want to know if this is just some glitch or the battery performance is still bad. But so far, my battery seems to be better than the last time.