find size of a index

sp_spaceused aaa
go
select * from sysindexes where id='229575856'
go
select (409*8) [clustered index]
go
select ( 248*8) [non clustered index ]
go



name rows reserved data index_size unused
-------------------- ----------- ------------------ ------------------ ------------------ ------------------
aaa 99999 5392 KB 3272 KB 2032 KB 88 KB

dpages reserved used
----------- ----------- -----------
409 674 663
248 256 251

(2 row(s) affected)


-----------
3272

(1 row(s) affected)


-----------
1984

(1 row(s) affected)

pl. give explanation as how is the size of the clustered index equal to the size of the table and hence what is the size of the non clustered index.