If somebody is selling that much from the sell wall, there are a few options;

1) He hates SMC;
2) He wants out from SMC but does not have time to check, and therefore sets a sell wall not to lose a lot but just some;
3) He is a newbie, does not know anything;
4) Lunatic.

Even if I need fast cash, I always try to put less sell walls, so that we don't scare people!