Its not really that simple. The ECU can adjust timing as hte engine idles. In fact this is how it fine tunes idle speed. The ISC motor is just a rough adjustment, and the BISS is only there to center the ISC while idling at the ECUs taget speed which is 750 unless you have DSMlink. So you can have timing off and still idle fine. This is how a few of my friends have lost motors. On 1g, any timing you add to base is also there at WOT. So if base timing is 10 degrees, you could be seeing 30 by redline even though your logger may report 25
I would spend 15 bucks on a cheap timiung light and get this right...