Tdi Idle speed adjustment

I tried to adjust my idle speed with VCDS-lite (unreg'd)

I got through to 'Engine', 'Adaptation' channel 2

I experimented with a few values and managed to drop it from 903 to 882 rpm

I was hoping for a bit more reduction (I live in London and spend alot of time at traffic lights

so I thought I'd boost my mpg a bit!!)

My question is what does the 'value' actually mean? I changed it from 32768 to 32743 - it wouldn't go lower.

I'd like to understand what I'm actually changing, if anyone knows. Are there other considerations here??

apart from just idle speed...

Is there any other way of getting it lower?

Thanks

Tony

2000 Octy tdi