Don't let mould cleaning products go down the drain?

[MooPointCowsOpinion]

Eh, how am I supposed to manage that then?

This is the stage I'm at: Sprayed on mould, product runs down wall and pools underneath mould, quickly stuff an old sponge underneath to soak it up, put plug in bath to avoid run off.

Now I'm supposed to wipe it off and dispose of it, but not down the sink?

How do I rinse it off the wall without it going down the drain?

Do they not just mean don't pour it down the sink rather thank the small amount you would use for cleaning.