select b.dbsname, b.tabname, hex(a.partnum), a.nextns, a.fextsiz FIRST, a.nextsiz NEXT, a.nptotal, a.npused, a.npdata
from sysptnhdr a, sysptprof b
where a.partnum = b.partnum
will give you a fine overview of number of extents per table together with their first extent size, next extent size, number of pages total(total number of pages allocated in extents), used (total number of pages used - ie one record in one page is 1 page used), data (total number of pages in data.
select * from sysextents will give you an extent overview per extent.
here you can find the chunk id (version 9.4)
prior to version 9.4, use hex(start). the first three positions are the number of the cunk. the rest is the offset in that chunk.