Time to learn about roman numerals.... Here is a handy clock if you are unfamiliar with them. Pretty much you need to know 1-7. 1 is represented with I, five with V and 10 with X. 4 and 6 and 7 is where it gets tricky. 4 is 1 before 5 - so its Roman numeral is IV. 6 is one after five so its roman numeral is VI.
Students also learned how to identify the charges of metals with more than one oxidation state using Roman numerals. Metals in the D, F, and lower P get Roman numerals - basically all metals but the S block, Aluminum and Boron get roman numerals. The roman numeral tells you the charge. We have to use this system because those odd metals can actually be found in more than one form - some with 2 possible charges - some with more than four!