Imports & exports under storage constraints and preallocations
It seems that you use the old export (exp) utility and not the datapump export expdp. For expthere is a parameter compress that manages the size of an initial extent of a table that is imported.  The default value is compress=y which means that the initial extent of the table (this is in most cases the space preallocated when creating an empty table) is as large as the space the table currently uses. So you should use the paramter compress=no. Then the initial extent of an imported table is as large as the initial extent of the table in the source database.