A voltage rail limits a gain stage without changing the filter ratio. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The ideal gain request is above the rail
Input 3 volts with gain 3 asks for 9 volts.
3⋅3=9
The rail limit is not a filter ratio
The upper rail is 8 volts, so the checked output clips to 8 volts.