Calculating the sum of one column divided by the sum of another column - keep getting wrong answer



I am trying to get a calculation that measures how many hours it takes to generate a lead. In my data I have 2 columns - one called "group hours" and one called "group leads"


In the best mode I have the formula set as:


`Group Hours`/`Group Leads`


I have added this value as a line (on a bar chart) onto a chart with this value reflected each month as an hourly value, so for example in November total hours = 82.56 and total leads = 6 so the answer using the above beast mode calculation should say 13.76 but instead it has the value of 24.79 which is incorrect.


Does anyone know what I'm doing wrong and how to get the value of 13.76?