this is "take with a grain of salt" caveat as this is top of the head stuff

You can create LUN up to max size in unity

when its initially created, it will take up 0 space + metadata space

As you write data and if you have dedupe enabled, it takes the inbound write and tries to do both

dedupe ( if a similar string is written to pool, simply create pointer to that )

compress ( if string is compressable ( emc 'secret sauce' algorithm it will compress )

so hence the lun written data may be smaller than written data.

For light reading, see https://www.dellemc.com/resources/en-us/asset/white-papers/products/storage/h16870-dell_emc_unity-data_reduction.pdf