I suspect it has to be an autobrake setting as maximum manual braking would be a variable
RMC, I'd be most gratified if you'd either (a) reassure me you're not a professional pilot, or, (b) explain why you think that maximum manual (should be pedal) braking is variable. It means pedals to the mechanical stops, usually before touchdown in certification flight testing. Thus system pressure goes to the anti-skid units, and brand new tyres and so on do the rest.