This message is just to let you know that there will be an upload schedule from now on.
Before, it was one chapter every three days, meaning one day on and two days off. That will not change, but now the days are fixed, they will be Sunday, Wednesday, and Saturday.
This is simply to fit Sundays as an upload day.
In fact, thanks to Saturday and Sunday being together, there will now be more total chapters and it will not affect the chapter uploads in general, it actually increases them a little.