Measurements at D17/D18 anodes opposite of instructions

[Whoopysnorp]

I am in the process of building two B16s, and I'm on the testing stage before installing the ICs. My voltages are measuring as indicated, with one caveat: when I throw SW1 to the right, I measure 0V at the anode of D18, not D17. When I throw it to the left, it's vice versa. This is the opposite of what the instructions say I should see. Was there a revision to this at some point that's not reflected in the instructions?