Custom Number Formatting

Hi

I have a chart that has five data series. Four of them are showing % changes and the fifth I need to show a ranking eg. 1 of 7

I need the ranking to appear in the data table of the chart so to do this I need to input a number in the source data. So as not to destroy the scale of the chart though I would like to input numbers less than 1 like 0.67 to represent 6 of 7 or 0.55 to represent 5 of 5.

Can anyone suggest a custom number format to just use the two numbers after the decimal point, and insert " of " between them?