Impdp 12c takes table original size
Typically caused by the segment attributes of the tables.

You can use TRANSFORM=SEGMENT_ATTRIBUTES:N, so the tables will be created with default options.

You can use TRANSFORM=SEGMENT_CREATION:N as well, so your segments will not be created at all, unless deferred segment creation is disabled in your database.

TRANSFORM

DEFERRED_SEGMENT_CREATION