What does e mean in shoe size?

Excuse me, could you clarify something for me? I've come across the letter "e" being used in shoe size, and I'm a bit confused about its meaning. Is it a specific code or abbreviation that indicates a certain type of shoe, size measurement, or manufacturer? Could you elaborate on what "e" stands for in the context of shoe sizing? It would be greatly appreciated if you could provide some insight into this matter.