If you ONLY have a single 4-port adapter, then you use
4a/4d Stack 1
4b/4c Stack 2
The card has two ASICs on it. One controls ports a/b and the other ports c/d.
This way is one asic fails, the stack does not.
Now, referring to the cable guide if you have more than 4-ports, you should use ports from all sources.
slots 0 and 4 for instance, you would/should do:
0a / 4b
4a / 0d
0c / 4d
4c / 0b