The MidX/MidY notation described on the wiki page seems to work just fine. Here's an example macro to demonstrate:
Found Image Token Example.kmmacros (35.2 KB)
In my tests, that macro moves the mouse right to the center of the KM icon on this forum. My best guess is that, even though the Find Image action only returns five numbers, the MidX/MidY notation automatically performs the math using the width and height values to derive the center.