Media Size compensation refers to adjustments made to the file to ensure accurate print output across different types of media (materials like vinyl, paper, fabric, etc.).  It compensates for the shrink and stretch, single sided as well as double sided. 

Media Compensation function is available in Layout and Editor.

Layout:  -> Edit -> Media Size Compensation

Editor:  -> click PMM -> 'Tape measure' icon 

- Select the Media compensation and click Print

- print the 1m square box and measure width and height

-  Enter values in Measured and the % of compensation is calculated. 

- if you use double sided, then after adjusting A, set B side and repeat. 

- The media size is linked to the pmm.  Every time this pmm is selected, the compensation to the image is applied.