stat reduc after lvl 15?

Someone had told me I can reduce my a level that is above 15 with a platinum sub. Is this true? If so where is the option to do it?

With a stat of 15, you can use a Platinum sub in game and it will reduce it to 10.

After, you need a Gold Sub in inventory, log off, and go to character manager to use that sub to reduce down to 1

( if you are wanting to go to 1 )

thanks