I am in the middle of building a control panel for a machine

All the retroarch stuff is working like a dream but I’m scratching my head with the fba cfg

I have my cp with two rows of 3 (let’s number them 1-3 on the bottom and 4-6 on the top)

What I am trying to achieve is have button 1, 4, 5, 6 and the 4 buttons used in the emulator, leaving 2and three unused.

Can anyone help?