Question Memory clock half of what it’s meant to be?

[ArchiePM]

I have an Aorus GTX 1060 6gb, overclocked to 2100Mhz but when I check MSI afterburner during loads it says the memory clock is 4151mhz, this is with a +150 boost on afterburner. On the gigabyte website it is said that this card does 9026mhz memory clock. Is my memory half the speed it should be?

 

[rgd1101]

ddr mean double data rate