In early medieval manuscripts, Indic-Arabic numbers were used for many of the abbreviations, probably because numeric shapes helped distinguish them from letters:
0 (zero or "o") - often used for grade/degree and ordinals (still used for this purpose by the 15th century)
1 - er/re/ir/ri/ra (still used for this purpose by the 15th c)
2 - ur/tur (still used for this purpose)
3 (which looks like z) - em/rem and occasionally us/um (still used, mostly for em or rem, but it's quite flexible)
4 (the old style 4 that is the same shape as EVA-l) was a superscripted apostrophe - see Post #42 upthread (this abbreviation fell out of use)
7 - sometimes used as an apostrophe (the old style, that looks like an upside-down vee)
9 - con/com and us/um (still used and very frequent)
5 and 6 were not commonly used. 8 was not commonly used as an abbreviation, but was sometimes used for d or s (especially terminal-s).
0 (zero or "o") - often used for grade/degree and ordinals (still used for this purpose by the 15th century)
1 - er/re/ir/ri/ra (still used for this purpose by the 15th c)
2 - ur/tur (still used for this purpose)
3 (which looks like z) - em/rem and occasionally us/um (still used, mostly for em or rem, but it's quite flexible)
4 (the old style 4 that is the same shape as EVA-l) was a superscripted apostrophe - see Post #42 upthread (this abbreviation fell out of use)
7 - sometimes used as an apostrophe (the old style, that looks like an upside-down vee)
9 - con/com and us/um (still used and very frequent)
5 and 6 were not commonly used. 8 was not commonly used as an abbreviation, but was sometimes used for d or s (especially terminal-s).