Ok, cool.
Got another question. What is 1 SW 1? Is that player 1's first button?
Yes, by default.
Remember - 1SW1 sends L Ctrl, but you can do a lot of other things if you wanted to.
You could wire Button 1 to 1SW1 and off you go.
You could instead wire Button 1 to 1SW3 (Space), reprogram MAME so P1B1 was Space in all games, and off you go.
You could instead wire Button 1 to 1SW4 (L Shift), reprogram the I-PAC so 1SW4 sends L Ctrl and off you go.
Finally, you could instead wire Button 1 to 1SW5 (Z), reprogram the I-PAC so 1SW5 sends R, reprogram MAME so P1B1 was R in all games, and off you go.
I am just trying to point out that the input labels are guides, you don't have to really use them.