It means to take filtered water if u have it. PH the water to 6.5-6.8.
Then pour it in untill it all drains out of the bottom.

Then do it again.
Not to sure how much you should do it, but basically u attempt to "flush" out all of the nutes u put in.

p.s. never heard of anyone putting the ferts right on the dirt. dosent seem like you would get a good mixture by doing this. my 2 cents.