The figures 0-9, introduced into Europe from India, via the Islamic world, around 1100. From the thirteenth century on, the use of Arabic numerals increased, partially supplanting Roman numerals and other alphabetic systems of numeric representation. They did not come into general use, however, until the fifteenth century.
Michelle Brown, Understanding Illuminated Manuscripts. Malibu, CA: J. Paul Getty Museum in association with the British Library, c1994.