CRATE Incremental Snapshots : Https://

We are using Crate 2.1.6 and i am bit confused with below statement

" Snapshots are incremental . Snapshots of the same cluster created later only store data not already contained in the repository"

My table is partitioned by a date column and every time i take a snapshot i think it always back ups the entire table. I am saying this on the basis on size if the snapshot on the filesystem and from sys.snapshots table

any suggestions would be appreciated.