@Jamie_Gonzalez this is directly from IAME USA East website under the tech documents.
"Play between piston and liner must be
0.11 ÷ 0.12mm. If play is higher than 0.14mm replace piston.
Pistons are measured at 17.5mm from bottom.
Size of liner to be matched with piston is marked on
top of piston with a green or red dot or with letter V or
If the size on piston top is marked with:
-a green dot or letter V: add 0.01mm to size marked
on the piston to match the liner size.
-a red dot or letter R: add 0.02 mm to size
marked on the piston to match the liner size."
I hope this helps. Attached is the link to the overhaul manual directly from IAME.