i rolled one grief in phase blade with +40% IAS and the other with +30% IAS

i wear the +40% IAS wepaon in the main hand, the left weapon slot in game.

now the IAS calculator shows me the IAS for the second weapon doesn't matter and that i have maximum attack speed.

is that correct or am i using the IAS calculator wrong?

do i need to roll another grief or is my +30% IAS grief ok as my offhand?