Honestly, your numbers don’t seem too far off from what others are reporting. iPads do tend to drop health a bit faster early on, then they stabilize after a while. Cycle count, usage habits, and even software updates can all make the percentages look inconsistent.
I’d keep an eye on real-world performance more than the health number itself — if it still lasts long enough for your daily use, you’re probably fine. If you want a bit more insight, feel free to check my bio for how mine has been holding up.