That's kind of my point. I can do it quicker with less chance of making an error by thinking 1024 + 512 + 64 + 16 + 8 + 4 + 1 (for example), than I can by working out "above the red line, above the orange line, below the yellow line, bellow the green line, above the blue line, left of the red line, right of the orange line, right of yellow line, right of green line, left of blue line, right of the purple line."

Then it doesn't really matter. A human (almostly) cannot calculate the checksum bits without electronic device. This table only helps a paranoid to cross-check, not generating.[/quote]
This is true. But you can use an open source SHA256 implementation on an airgapped device to calculate the necessary 4 or 8 bits and then work out the checksum word yourself, which is superior to trusting your wallet software.