cell flash cache read hits and bytes over interconnect

Hello,

I ran below statements on exadata.As seen below the number of cell flash cache read hits increased on second execution of the pl/sql.

However,the physical read total IO requests increased from 813 to 1015 - query being the same.Could you please elaborate more on this?

SQL> conn sales/sales
Connected.
SQL> declare
a number;
s number :=0;
begin
for n in 1 .. 500 loop
select cust_credit_limit into a from customers where cust_id=n*2000;
s := s+a;
end loop;
dbms_output.put_line('Transaction total = '||s);
end;
/  2    3    4    5    6    7    8    9   10   11

PL/SQL procedure successfully completed.

SQL> select a.name,b.value from v$sysstat a,v$mystat b