pga_aggregate_target

I am trying to understand this parameter. Is it correct that the total PGA inuse (line 4) can exceed the aggregate PGA target parameter (line 1)? I thought line1 was fixed.

SQL> SQL> select * from v$pgastat;

NAME                                          VALUE UNIT
---------------------------------------- ---------- ------------
aggregate PGA target parameter             10485760 bytes
aggregate PGA auto target                   4194304 bytes
global memory bound                          524288 bytes
total PGA inuse                            13915136 bytes
total PGA allocated                        17977344 bytes
maximum PGA allocated                      17977344 bytes
total freeable PGA memory                         0 bytes
PGA memory freed back to OS                  131072 bytes
total PGA used for auto workareas                 0 bytes
maximum PGA used for auto workareas               0 bytes
total PGA used for manual workareas               0 bytes
maximum PGA used for manual workareas             0 bytes
over allocation count                            37
bytes processed                              602112 bytes
extra bytes read/written                          0 bytes
cache hit percentage                            100 percent