Extra Size Shoes

What does it mean when a pair of boots are marked with a width of additional classification EA + large?

Most "regular" shoe size are sometimes B or C width. The higher the letter, the entire shoe (much like hat sizes). A narrow, B is average, C is a bit wide, wide D, E is extra wide, and then they just start adding Es, EE, EEE, EEEE, etc. Most people are width B.

Another system is N (narrow), M (Medium), W (Wide) WW (Extra Wide), WWW ... and so on.

its wider than regular shoes for PPL with wide feet (like me)