Actually PGA allocated > PGA_AGGREGATE_TARGET ?

The following is my query result against v$pgastat view. PGA_AGGREGATE_TARGET is set to 1G. According to Oracle' documentation, Oracle should attempts to keep the amount of private memory below the PGA_AGGREGATE_TARGET specified. But from the following it looks Oracle allocated 1.2G PGA memory, and the maximum PGA allocated is 1.3GB which is far above 1G (PGA_AGGREGATE_TARGET), I am confused. Could anyone share some light on this?  

aggregate PGA target parameter

1,073,741,824.00

bytes

aggregate PGA auto target

85,053,440.00

bytes

global memory bound

107,366,400.00

bytes

total PGA inuse

984,952,832.00

bytes

total PGA allocated

1,259,997,184.00

bytes

maximum PGA allocated

1,347,652,608.00

bytes  

Thanks,

Lu

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