The drawing on the left looks to be wired in parallel and the one on the right in series. So if you have 2 4ohm subs wired in parallel they should be running at 2 ohms.
And is the diagram of your amp accurate? I've never seen a mono amp that you connect the far right negative and far right negative. From what I've seen it's usually connecting the first 2 positive and negative inputs (from left to right).