Backup file size is significantly smaller than indicated occupied storage space on my iphone 12 pro max

Hi all,

I recently did an upgrade from my iphone 8 Plus to the 12 pro max. I completed the data transfer from the old phone to new phone and backup again on my new phone through icloud. and noticed the backup size is significantly smaller than the actual storage. I went to icloud storage on my new phone and check under Backups to see what been backed up. Here is some data to illustrate my point:

Backup size: 6.33 GB

Photo Library: 59.55 GB

Wechat: 1.74 GB

WhatsApp: 1.39 GB, etc.

I am just a bit concern because the backup file size from my old phone showed the larger file size than the backup size I have on the new phone. just wonder if it is normal to see smaller gb backup size. Even my photo capacity was more than it. just afraid, if the photos are not part of it if I restore from the backup file.

Any feedback is appreciated.

TIA. :)