allocation question

[GZ at MIT-MC (Gail Zacharias)]

Could someone explain the following to me?
:LISP<space>
LISP 2057
Alloc?n
(sstatus flush t)
(suspend ":pdump gz;ts test
")
The resulting GZ;TS TEST file has size 18 blocks.  Now I try:
:LISP<space>
LISP 2057
Alloc?y
# REGPDL = 10000	0
# SPECPDL = 4000	0
# FXPDL = 10000 0
# FLPDL = 2000  0
 LIST =  40000  0
 SYMBOL = 6000  0
 FIXNUM = 14000 0
 FLONUM = 2000  0
 BIGNUM = 2000  0
 ARRAY = 1000   0
(sstatus flush T)
(suspend ":pdump gz;ts test
")
The file that results  from this is 21 blocks, i.e. larger.  If I do
(gc) before the sstatus, I get 16 and 19 blocks, respectively, still larger
despite all those 0's.  Thanks.