Report Builder – graph report missing C: drive

Report Builder – graph report missing C: drive

Hi,
Report builder graph report is not showing all the server partitions, in this case C:\ partition is missing as opposed to table report. 

Table report - shows C:\ and D:\


Graph report - showing 88% which refers to D:\ 
And is it possible to have the instance name?

                New to ADSelfService Plus?