Only Iran knows how long they've been enriching uranium and how many centrifuges they have. Can anyone believe anything they say? I think not.
Let's give them the benefit of the doubt and send them one anyway...
I suspect the announcement was intended to slow down any impending attack. With 164 centrifuges it would take years to accumulate enough bomb grade material. If, however, they are actually running 4000 then they likely already have enough or will very shortly.
If you believe their public statements then we have lots of time to deal with them. This will reduce the urgency in the minds of the international community giving Iran a chance to build a number of bombs.