Don't believe anything just because somebody said so.
Especially when there's conflicting information.

Check the datasheet, and test it for yourself. Then you will know the truth.

This program will help with the testing part.

Code:
Volume   VAR BYTE
Vstep    VAR BYTE
Result   VAR BYTE
Carry    VAR BIT
HIGH PORTD.0     ; initialize serial line
PAUSE 100
FOR Volume = 5 TO 0 STEP -1
    FOR Vstep = 5 TO 0 STEP - 1
        Result = Volume - Vstep
        Carry = STATUS.0
        SEROUT2 PORTD.0,84,[DEC Volume," - ",DEC Vstep," = ",DEC Result,"   C = ",DEC Carry,13,10]
    NEXT Vstep
NEXT Volume
STOP