Hi there Mahinder Choudhry,
We’d like to start by clarifying how the maximum capacity of the battery in your iPhone relates to overall battery health. To start, it’s normal for the maximum capacity percentage to decrease over time. This is because all rechargeable batteries are consumable components. The rate at which it decreases is dictated by usage and many other factors. Check out the ‘Your battery's maximum capacity’ section in this link to learn more: iPhone Battery and Performance - Apple Support
A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions.
Keeping that information in mind, 89% maximum capacity indicates the battery in your iPhone is still in good health.
Take care.