Automatic shared pool management

Hi,

One of our test databse in In automatic shared pool management SGA_TARGET=800M and SGA_MAX_SIZE=800M

1) I can see shared pool usage is around 625 M and shared pool allocation is arund 800 M in average when SHARED_POOL_SIZE= 0
But I can see shared pool usage is around 325 M when and shared pool allocation is arund 400 M when SHARED_POOL_SIZE= 350M.

Now I shall like to ask below question  :

A) How can the shared pool usage become so small when there is a minimum setting for shared pool size in comparison to the  shared pool usage when SHARED_POOL_SIZE= 0  for the nearly same sqls run and in the same duration .