Haven't explored how high the subscale goes, but the FAA has a procedure for QNH above 31" (1049 in civilised speak) so it may be not unheard of:
g. When the barometric pressure is greater than 31.00 inches Hg., issue the altimeter setting and:
1. En Route/Arrivals. Advise pilots to remain set on altimeter 31.00 until reaching final approach segment.
2. Departures. Advise pilots to set altimeter 31.00 prior to reaching any mandatory/crossing altitude or 1,500 feet AGL, whichever is lower.
PHRASEOLOGY-
ALTIMETER, THREE ONE TWO FIVE, SET THREE ONE ZERO ZERO UNTIL REACHING THE FINAL APPROACH FIX.
or
ALTIMETER, THREE ONE ONE ZERO, SET THREE ONE ZERO ZERO PRIOR TO REACHING ONE THOUSAND THREE HUNDRED.
NOTE-
1. Aircraft with Mode C altitude reporting will be displayed on the controller's radar scope with a uniform altitude offset above the assigned altitude. With an actual altimeter of 31.28 inches Hg, the Mode C equipped aircraft will show 3,300 feet when assigned 3,000 feet. This will occur unless local directives authorize entering the altimeter setting 31.00 into the computer system regardless of the actual barometric pressure.
2. Flight Standards will implement high barometric pressure procedures by NOTAM defining the geographic area affected.