The picture I'm looking at here shows -25 on it (not +) so I assume it's -90 to 0 like most AVRs today (Marantz can be set either way. I've looked at about 20 different photos and they all show negative numbers on the front panel. I like the reference at 0 as it makes more sense to me. It does go positive on the Marantz 7012 I'm using, but that's amplified pre-amp values. 0 is maximum "passive" before the amp in the preamp kicks in. It goes up to +18 I think.
-35 would be pretty low volume after calibration, I think. I watch most movies at -6 to -11 here (I've watched a few at 0, especially Disney titles that seem lower level). Some compressed music needs to go back towards -18 or so. Uncalibrated is anyone's guess.