Nanowrimo is fairly loosely structured and it's really all up to you in the end. The main question is would you feel guilty using those 800 words towards your end goal even though you know it won't be included in the novel or would you still feel accomplished at the end knowing you wrote 50,000 words in a month even though not all of them were included in the finished product?

Me personally, I would probably discard those 800 words because they aren't being used, but on the other hand, I have included scenes that I knew weren't going to be used in a novel because I learned something about the character. That scene just never actually fit into the working rough draft. So, it's really up to you.

Good luck!