Ancient Mathematical Mystery

Integer Repetition Table
Click to embiggenate
The numbers in the last two rows of the Minus chart (left) have decimal points

We're watching Hooked and this odd poster shows up in one scene and I've been trying to figure out just what it's for. I got one clue from reddit:

It seem to be a educational poster used in elementary school in early 20th century. There is a book published in 1904 explaining how to use the board called "Kokonaislukujen kertaustaulun selitys ja tulokset" by Hultin, Hj and Reinhard, Ph.

Google translates the title to "Explanation and results of the integer repetition table". That's all I've been able to find. If anyone out there has a clue as to how to use this table, please let me know.