@Amit Vengsarkar
The RHEL VM you are using has LVM setup, which is why you are seeing the difference. I am guessing this is using an image which was imported from an on-prem VM. I normally don't recommend using LVM in the cloud as it increases the complexity without benefits. If you wish to expand the root LVM partition this is a helpful guide, this is for Ubuntu, but should be the same across Linux. I highly recommend using a non LVM image, but if that is not possible then the guide can help you familiarize yourself with the management of it.
Hope this helps. Let me know if you have further questions or issues and I will do my best to assist.
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