This errata applies to the Classic Reprint of Man, Myth & Magic, although it could also apply to the original boxed set books. PDF version, page 24 of Book 2 (PDF page 51)
Print version, page 48
All references to 2d20% should be read as a percentile (or D%) roll. Any version, page 7 of Book 1 (PDF page 10)
The building marked “T” should be “L.” Any version, page 18 of Book 1 (PDF page 21)
The second paragraph under “Contests” refers to an Arena Map. This can be any tiled or hex map, either blank or something you customize to your own preferences (rounded, square, oddly-shaped, etc.). Some versions of the original 1982 edition corrected this to read, “Both you and your players will need to make a special Arena map... to make this map just grid off a sheet of paper in 1/2 inch squares.”