@WeebBros Sometimes the first, sometimes the second. Commonly they're used to judge a mangaka's ability, and see if they are worth serialising. If the one-shot is really good, though, they'll serialise it sometimes.
I've never commented on a manga before, but this broke my heart so much I just had to
It's so fucking good, I hope the mangaka gets the recognition they deserve
I find it fascinating that all the comments in the general comment section praise this, and almost all the comments in the chapter comment section are conversely more or less blasting it as a cheap shot to the heartstrings with no real depth.