At the beginning of the Gothic period, the main system of writing numbers used was the Roman numeral system. This system had been widely used across Western Europe since the Roman Empire. However, toward the end of the Gothic period Arabic numerals began to be widely used. This was largely due to the increased trade with Arab traders beginning around the 11th century. By the 14th century Arabic numerals were in wide use, and eventually became the number system of the Western world.
Example of Roman numerals, circa 1185-1199 CE, at bottom of page:
Image credit:
Berkeley, University of California, Berkeley, Bancroft Library
UCB 016
http://scriptorium.columbia.edu/
Another example of Roman numerals, circa 1290-1310 CE:
Image credit:
Berkeley, University of California, Berkeley, Bancroft Library
UCB 130:ff1300:26
http://scriptorium.columbia.edu/
Example of Arabic numerals, circa 1440-1460 CE:
Image credit:
Austin, University of Texas at Austin, Harry Ransom Humanities Research Center
HRC 043
http://scriptorium.columbia.edu/