The bit above the table is key - ChannelA = slot 2 and slot 4, Channel B = slot 1 and slot 3.
So you need to use a slot from both of those channels, i.e. slot 2 and slot 1, or slot 4 and slot 3 (which is what the diagram below shows, for 2 modules use either DDR4_2 and DDR4_1, or DDR4_4 and DDR4_3.