Adjust space character in spritefont

Hi all,

I've made my own spritefont and want to adjust just the space character width. I've tried searching but can't seem to find anything apart from spacing data code which I can sort of understand but don't see a SPACE reference anywhere. Do I just put [2, " "] and do I have to add a blank cell in my spritefont PNG?

Thanks for any help

Anybody?