What is the meaning of: "331 regression corrections"?
331 more, or less cases?
They have been doing this for a few days now. Basically those are backlogged tests that now have their result coming back. But instead of counting them as confirmed cases on the day that the results came back Taiwan instead insists on counting them as "regression correction" and update them to the case total in previous days.
Basically it means the case numbers for last few days will always be wrong, because they will be "regression correction" updated at some future date. Regression correction is already a meme in China with people saying:
Girl: how many previous girlfriends have you had?
Boy: one.
After marriage
Wife: wait, I thought you said you had one previous girlfriend?
Husband: there's been a regression correction of 19
Taiwan today: we have zero new confirmed cases, we've beaten COVID-19!
Taiwan in a week: there's been a regression correction of 700 cases for seven days ago, on the plus side there are zero new cases today!