Messages taking up way too much space in iCloud

Messages only takes up 2.17 GB in my iPhone's local storage and 2.63 GB in my Macbook's local storage. But Messages take up 12.3 GB in iCloud. Why is it so much more? Shouldn't they all be equal? Is there some way to fix this?

This is also after I went through and manually deleted a bunch of my largest attachments in both devices, which I'm not sure why I had to do separately in the first place, as they shouldn't be independent since they are both supposed to be synced to iCloud.