First ASDA is always the same! This is a fixed value, unless the runways gets longer when it is wet
Your max take-off mass gets lower for the same runway length.
In order to make the MTOM penalty less, the usual screen height of 35 feet is reduced to 15 feet only, hence a longer part of the runway may be used for the takeoff roll up until VR.
Which is by the way interesting, when people say it's safer to take wet runway performance calculations for a damp runway, sometimes you end up assuming and derating even more.