Epson CX6500 Reference Manual page 49

The graphic displays the amount of ink that was remaining when
Epson StatusMonitor was first opened. To update the ink-level information, click
Update.
If any one of the ink cartridges that are installed in the CX6500 are broken,
incompatible to the printer model, or is installed improperly, the Epson
StatusMonitor will not display an accurate calculation for the amount of ink
remaining in any of the ink cartridges. Be sure to replace or reinstall any ink
cartridge when indicated by the Epson StatusMonitor.
For Mac OS X
Double-click Macintosh HD (the default hard disk name), double-click the Applications folder,
then double-click the Epson Printer Utility icon. The Printer List window appears.
Select the CX6500, then click OK. The Epson Printer Utility dialog box
appears.
Click the Epson StatusMonitor button. The Epson StatusMonitor dialog box
appears.