RPM scaling, is a % of the active warm up enrichment bin at highest RPM. If you set this to 75%, at say 6500rpm, the added warm up enricment is 75% of the active bin value, but at idle, it will be 100% (actual bin value) everything inbetween is scaled. Not too sure if it scales the whole value, IE 75 % of the bin value for example of 140%, or whether it reduces just the 'extra' portion of the bin value (140 - 100 therefore 40%)
Driving at higher RPM when the engine is cold, the actual amount of extra fuel requirement is less. If after tuning the warm up enrichments, the engine goes rich when cold, at higher RPM, reduce the scaling value