Epson ColorPage EPL-C8000 User Manual page 74

7. Slide the edge guides until they just touch the edge of the stack
of paper. Make sure to adjust the small edge guide so that it
points to the size mark that matches paper loaded.
Note:
The printer automatically knows the size of loaded paper from the
position of small edge guide, so you need to adjust it the correct
position.
3-18
Paper Handling