Compression decreasing the freespace

JamesMichaelRaj

When i compress a table in oracle using (ALTER TABLE Table_Name MOVE PARTITION Partition_Name TABLESPACE table_space COMPRESS) query.

When we compress a table, freespace should be increase...ya for some table freespace is increasing...

For some table freespace is decreasing.

instead of increase in freespace,  compression decreasing the freespace.

Why freespace is decreased for compressing some table ?What is the reason?