What does this approx. 300-year-old Korean text by Choi Seok-Jeong say?
Here is my transcription into an ROC/HK standard character set.

《九九母數變宮陽圖》
從？皆得九十數總積八百一十母數
本宮圖即甲編母數名圖此圖自本
宮而一變
橫看從看
九數無一
重複者〇
以下四圖
係新定


I have a feeling the second character ？ is「衡」.
Please be wary of phonetic loans. For example,「從」might be better off being interpreted as「縱」. With the above, you have the two characters as「縱衡」(vertical and horizontal).