Who does the checking?

We received the first order of a popular calendar used by congregations yesterday. The calendars were right on schedule arriving just about the same time that they did last year.
We were preparing to ship about a dozen of them to various customers when Cara on our staff noticed something strange inside. The month of May contains all of the liturgical feasts and fast days and other information. That’s good. But, why does the month look strange? Oh, there it is. The numbers for each day of the month are missing!
May 5th, my sister's birthday, is which day? There is no way to tell on the calendar. This is not helpful.
Immediately I contacted the publisher. They replied today, in part, “Thanks so much for bringing this to our attention. This is a manufacturing error and we’ll have it redone as soon as possible.”
It was a topic of repeat conversation amongst our small staff yesterday. So who does the checking of a calendar before it is shipped to retailers? Anybody? It seems that it would be a prudent activity.
Every package that we ship to a customer is checked by someone other than the person who filled and sold the order. And still, some errors slip through.
I wonder how large was the print run for that calendar? I wonder how long it will take the publisher to “have it redone.”