Setting it smaller than 1.0 makes it faster. Setting it higher makes it slower.
So if ItemConvertionMultiplier=0.500000 then a item that takes 10s to craft will take 5s.
ItemConvertionMultiplier=0.500000
If ItemConvertionMultiplier=2.000000 then that same item would take 20s.
ItemConvertionMultiplier=2.000000