Numbers Calendar template

How do I use the Numbers Calendar template?

When I change a day number, it seems to try to change the numbers of the days but doesn't do it correctly.

Can I somehow change it to a new month and year and get a calendar for that month and year?

In another post, someone said there were a bunch of hidden rows that are involved in the automation. When I go to "table" in the app menu, it doesn't indicate there are hidden rows. Are they secretly hidden? How can I see them?