470 8gb overclocking undervolting for low temp

Hello everyone
I recently added a 470 8gb in my rig.
The temperature i get is around 55oc but in reality the temp is a lot higher (probably the mem temp).
Here are my settings


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What setting should i apply for decrease the mem temp.
I guess it has to do with mem undervolting

Put the 800 to memory controller voltage. Not mem voltage.