Delete rows from fact table

Hi,

I've done a delete selection from cube X for year less than 2010 (because this infocube has data since 2003). I want to reduce the records number in the infocube, but after delete selection the fact table has the same number of rows (greater than 47 million of records, I check infocube size using program SAP_INFOCUBE_DESIGNS)

Why the number of rows in fact table is not reduced? How can I reduce the number of records in order to improve the query access to infocube?

thanks in advance,

regards,