Yeah, it looks like both of the brakes you linked to on ebay do NOT have removable fingers, which would let you bend the third and fourth sides of a box after bending the first and second(opposite) sides.
I have one like the 2nd link, but it does have removable fingers-even then, they are only in 1 inch increments.
And actually bending a box using a "press" type brake like that is not very doable-you will run into clearance issues.